When your tomato plants get frosted they will die (or at least start a quick downward spiral). It is good to get all of the usable fruit inside before then (the fruit might still be usable after a frost - it probably will not freeze, but I don't see too much reason to wait). The sun angle, shorter cooler days, and longer cold nights are all working against your tomato plants - there is a point at which they seem to stop and wait to die. If it is not going to get warmer your tomato season is probably over.

You can pull the tomato plants with a bit of a root ball intact (knock the dirt off) and hang them in a shed, it is amazing how many of the fruits will ripen this way (I grow mostly paste types, different varieties could behave differently). There is a bit of a problem doing this even if you have the extra space, the ripened fruit is of decreasing quality and at some point it will be best to compost them.

I hope this helps, best of luck!

Soon as it is dead or it stops baring.

If I still have some fruit, I try to leave it on as long as possible (as long as the plants are healthy and not diseased) I think the maters taste better vine ripened. I try to pick the outer maters if there is a light frost coming. The ones inside seem to do just fine and keep ripening on the vine.The foliage keeps the frost off.
I'm also in No CA where we are going to be having upper 70s this next week and mornings into the low 40s. It's hard to tell!
I've had tomatoes into Dec and Jan (rare) and kept growing them "just because I can".
This year I'm going to pull several that aren't producing anything and just keep a couple to see if I get anymore.
Nancy