How often do you have to mow acreage with a zero-turn riding lawnmower?

Grass grows no matter what type of mower you use. I will say the ztr I had did not mow tall grass as well a normal one.

the time between mowings has nothing to do with the mower, it has everything to do with how fast the grass grows, is it wet or dry, sunny or cloudy, everything effects it, i would say once a week if you want it to look nice, once a month might work if you are just trying to keep it something below a cows belly, every other week if you want it less than knee high. in dryer climates . less often

It all depends on what type of grass you have.

For example, in the Pacific Northwest, we have a lot of Rye-grass and Fescue grasses, which thrive at 2-3 inches of height, anything less and the grass dies.

I would always try to mow when the grass is 33% more than the peak height of your grass. So for me, I tend to mow the grass when it is about 4 and a half inches high. In this way, you are getting the best part of the grass, the top third (which stores all the nutrients) and put it back into your lawn, thus making it grow stronger.

Hope this helps! It might help to find out what type of grass you have. There are many different websites for telling you what type of grass your area has the most of.