Prohibit Equipment on Lawns?

For those of you with a ZTR and WalkBehind, do you prohibit your machine on certain lawns?

Example:

Do you keep the ZTR off smaller lawns?
If so, what is the size of lawn that you prohibit the use of a ZTR? Smaller than 10,000 square feet?
Smaller than 20,000 square feet?
Etc...

I'm finding more and more people wanting a WalkBehind ONLY on lawns that are 20,000 square feet or less.

I can see where some lawns will wear in certain areas (using a ZTR) after continuous weekly service, but every lawn is different.

I believe the extra 500 lbs or so is the cause. Meaning the WalkBehind will not wear the grass out as easy as a ZTR.

Most lawns smaller than 20,000 square feet take me longer with a ZTR anyway b/c you have to be so slow/smooth/careful when turning. So it doesn't bother me too much to use a WalkBehind on those yards.

Tell me what you all think!!!

-Thanks