not that long, may be 6 months? but a pole is a must for the vines to adhere to, otherwise the leaves won't increase that much. also it'll need a very good dappled sun-light indoors. outdoors it'll grow faster and bigger even in shade.
and very importantly, it needs to be quite warm: 75F-80F with at least 70% humidity optimally to grow really fast. if you drop below 70F (and that includes night temps) it'll slow down considerably. at 65F it just stops growing (roots too cold) - it's a tropical plant after all.

Hey Petrushka! Good to see you! :)

Do you make your own poles,and if so,any tips from past experimentation?

i just clipped with butterfly clips to the metal strut (the shelving) and let it grow up towards the window and creep along the window up. it's wedged in the corner and still trying to grow up :).
it would be great to get just a 'bark sliver': a flat piece of trunk with bark. i don't know what to call them, the pothos and philos used to come attached to the them. the roots can really attach to bark nicely. but i don't see them at all anymore. nurseries should have them.
otherwise a fat bamboo pole would do with some coir fiber (the matting) wrapped around the pole with zip ties (pvc pipe will do too): the roots will grab it, especially if you mist the coir slightly from time to time.
my leaves did increase in size, may be doubled? from growing this way. and the vine grew may be 6' in one year.
i've been thinking of making a pvc pole, but the problem is how to position it securely in the pot, so it won't tip over?
the bark slivers usually sit nice and tight in the soil, but eventually the bottom rots.
i've seen 'the baby leaves' grow to 12" just on a 5-6' rough trunk about 1.5" in diameter (a sapling) - but that's in tropics and in shade house conditions of warmth/light/humidity.

The one in the picture has mold growing on the wooden pole and roots/vines of the pothos.

Why does that happen and how can it be avoided?

cool temps and damp. looks like the office in the pic. if at night temps go below 68F, it could do it. reduce the watering in that case.
hi, asleep! i am myself nodding off a bit ..:::).
can't say that i've tried it, but i saved the post from the guy who swears by it: grapefruit seed extract (Nutribiotic Gse Liquid Concentrate). he sprays it on the surface and it kills the mold.
i had slimy mold on bark and used mild solution of vinegar (2tb to a gallon) - sprayed on the surface sev times. it worked.
bark and soil should be ok, roots? am not sure ...
if you have rubbing alcohol, dilute by 2/3 with water - it should do the trick. on roots may be try 1:4 water...just to be sure.
i've done that on leaves for mildew, it kills it, but if you do it sev times and leaves are tender, they might dry up . but epi should be ok as far as leaves go. again, am not so sure about roots.
you can try spraying it on a small root area - if the root darkens / dries up or rots, then it's not good.

I shoulda asked if they had coir when I was at a florist's a couple weeks ago.

DID finally get my hands on some long fiber sphagnum though(meant to get that a LONG time ago but have it now).

Any suggestions?
Tube made from hardware cloth stuffed with it?
Mix anything else with the sphag?
Would bark be a bad idea for mold/fungus reasons?

Can't say as I've ever really made one before.

i won't use lf sphag - it's soft, the tube won't stand - you'll need to put at least a stake thru it, even with hardware cloth. and it will disintegrate rather fast.
coir fibre webbing/matting (what they use to make liners for wire baskets) is MUCH stiffer. and it also keeps much longer (sev years), especially when NOT wet continuously. it also does not shed like sphag all over the place and rewets in second. if sphag dries up - misting won't rewet it. i know they sell sphag stuffed tubes for some epi's - to root plants in them, but for support tubes i wouldn't use it.

Sweet!
Good info there,thanks!

So all the coir I've got is currently in use lining my staghorn fern's basket. Where exactly does one go to get the kind of volume we're talking about necessary to wrap a stake with? Stake will likely measure about 4'. If all that's available is basket inserts,I guess I could cut one into a long ribbon and wrap it around,then secure it with fishing line...?

Just thinking out loud here.

in my nursery they sell it by the foot. that's how i buy it, but they always run out by the fall and only stock up for the summer.
it's not exactly cheap, but i can't buy in bulk, 'cause i have very little storage in an apt.:((.
search for coco fiber by the yard and look at images - you'll see what i am talking about.
this is a link, cheaper one is 2'x10' for 20$

Here is a link that might be useful: coco fiber roll

Thanks for the heads up and the link! You are right...that IS a little pricey. I'll have to see what I can't come up with locally. Money's pretty tight right now.

Hi petrushka. Do you know how long a pothos plant is capable of growing? I need a plant to grow over a trellis and drape down to the ground creating an enclosure of greenery. Do you think pothos would do this or would another plant be more appropriate? I plan to grow this indoors. The trellis would be suspended over my bed and watered with hydroponics with an LED array above it - thanks for any advice.

no problem at all - it can grow that long. i had it in pots near the headboard and it grew up over the bed canopy and along the poles towards the end of the bed and hanging down :) . so that's like 10-13 feet. it can certainly grow longer (and pretty much indefinitely :)). the only problem is if you let it dry out often enough it'll start dropping lower leaves and look kinda bare and ugly near the pot. so hydro set-up should help prevent (with liquid fertilizer of course).

with good lighting and close to 72-75F it grows fast enough, but not super fast.

i think it's the best indoor plant for what you want to do. good lighting is a must though - i keep mine growing in West window 1 foot away from the window - so it gets partial sun and it still grows towards the glass. wanting more.

before i had it in the room with 2 walls of glass - 10 feet wide each, facing east and south . but it was 6 feet up on the roof of the bed creeping towards the south window, so out of direct sun, but very bright. that's the key to fast growth.

and warmth of course.

in southern room i had 80F even in winter on the sunny day with all the low sun. so that's a factor. if you keep your room below 70F it'll grow quite slow.

"Pothos around the room"
https://www.google.com/search?q=pothos+around+the+room&source=lnms&tbm=isch&sa=X&ved=0ahUKEwiDofTmjNXUAhXL6SYKHZKsDjcQ_AUIBigB&biw=1088&bih=458#tbm=isch&q=pothos+around+the+room&nfpr=1

There's a ferry terminal on Alaska's Marine Highway that has (or maybe "had," by now) a single strand of pothos wrapped all the way around the interior walls. It must have been about 400 feet of pothos. I don't recall the town, Ketchikan, maybe, or Wrangle.

Thanks Barbara and all. Much appreciated.