My gangmowers are set to cut 1.5". I never adjust cutting height but do check blade/backplate gap every time I use them.
Depending upon how bored/busy I am when I tow them, I'd guess between 60 and 90% of the strip is cut to that height. (Busy/bored - tend to pull them faster and they become less efficient) In summer I tend to cut it every 10 - 14 days, but really that is because it looks neater and keeps the clover under control.
If the grass is too long - it hides dog and pony pooh. If it is wet it makes decelleration tricky, too!
Stik