How often do you guys do it or how many miles?

Once a year, normally in the spring after the hunting seasons are over.

Just depends on how much your ride it but once a year is usually good. I trail ride in Arkansas quite a bit so at least twice for me and cleaning/changing air filters each trip.

I use ATVs and side by sides for work. I currently own 8. We change the oil every 150 hours or once a year whichever occurs first.

Usually once a year, in Spring after temperature stabilizes a bit.
If stored over winter, moisture seems to condense in engines more with the temperature swings.
If you use it year around, the motor heat will burn off the the moisture.

I change mine every September.

I was hesitant to change the oil in my low miles Yamaha side by side before this deer season as the oil in it only had 500-ish miles on it.

Afterwards I was glad I did as the oil that came out did have a metal glitter to it.
Nothing terrible, but defiantly not something I needed to be pumping through the machine.

BTW, my Polaris Ranger never failed to provide glittery oil when changing it.
My Polaris 4 whlr not soo much.

More often is evidently a better option if you like to keep them a long time.

Once a year after season is over. In my opinion that should be adequate unless youre really putting some miles on it.