If there are roots emerging from the drainage holes then it probably needs repotting into a six inch pot.

I have my Beaucarnea recurvata/Nolina in a mix of commercial potting medium - pine bark and fines with a good proportion of pumice, a serving of six months slow release and NO water crystals, with an extra serving of 5mm river grit, fairly sharp.

It gets treated like a cactus - watered once a fortnight or less, so it isn't a lush specimen but does tolerate light frost. (Has to. It lives at the edge of the porch.)

Slow release once a year - a mean teaspoon full sprinkled on and stirred into the surface. That's for an eight inch diameter fifteen year old plant in an eighteen inch high terra cotta planter. Sun for most of the day but the temperatures are moderate. Below 100F over summer, though the UV is often very high.

I cheat on the watering: there are some little weeds in the pot I know to be drought tolerant. If they're starting to look miserable - it's time to water.

Remember, even when the top couple of inches are dry, the bottom can still be quite damp. While the plant is still in a small container go more by the weight of the container than the appearance.
Dunk the plant, wait for the bubbles to stop, lift it out, let it drain - then heft it. That's how it feels when fully watered. Then check week by week and notice how the pot is getting lighter.

Ensure it never stands in water. Some discreet feet in the saucer should give enough protection for the roots at the bottom.

I'd like to add, if you do repot, not to go from a 4" to an 8". That's way too large..also, I'd wait till spring to repot. Ponytail's really slow down in winter so hold off till spring. Toni

Here's a picture of one of mine.

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It's small also. it's in a three inch pot. They grow very slow. I've had this one for two years. My trick for watering, if I think it needs water, I wait, because it doesn't! They like light. I keep mine outside in the summer. I use a general house plant fertiliser every other watering in the summer. No fert in the winter. If the soil drains well, it should be ok. They don'tlike wet feet.