I cut the farm that I live on at least twice a year. Part of it (visible from my home) I like to cut more often so the wife has a pretty view when she drives home.
It's my Father in laws farm (although we own several acres in the middle of it) and I cut about 100 acres give/take. I don't really know the size other than what he has told me.
They (and therefore I) used to cut it with a 35 HP International with a 5' mower hanging off the back. Talk about a major pain in the hiney!
I finally stopped "helping" since it wasted one of my summers. They have finally brought a 85hp machine home and a 10' Rhino. Now it's a world easier to cut.
During the time I went on strike, realizing my free time meant more to me than wasting my summer cutting someone elses land (using their tractor but I usually bought the fuel) it went uncut for maybe 3 years.
There were saplings growing up EVERYWHERE and as has been said, it was a lot harder to cut it back.
I did it though, suffered through a couple flat tires thanks to little sapplings piercing them. Now that it's been beat down for a couple years it's much easier to maintain.