That is a really tough question to answer because there are a HUGE number of variables that come into play: how thick is the paint system, how much can be removed from the paint system before compromising it's long-term durability, what methods are a being used to apply M205 (which greatly affects the amount of material removed) and so on and so on.
Generally the clear coat on your car is going to be about 2 mils or 50 microns in depth. On a daily driven car which is exposed to UV light you don't want to remove more than 15-20% over the life of the car. So the maximum amount of paint you can polish away is roughly .4 mils or 10 microns. Luckily most swirl marks are less (far less) than .5 mils or 2 microns deep. So you should be able to fully remove swirl marks at least 5 times on most paint systems.
It is hard to determine just how much material is removed every time a particular product is used. Some paints are very soft so a lot (realtive) of material is removed. So paints are very hard so very little (relative) is removed. Than we have the huge number of variables in the application methods. Are you using a rotary at 2200 rpm with a cutting pad, a Dual-Action polisher at low speed with a finishing pad? By hand? Changing application methods could affect the amount of material removed (and thus the amount of time something could be used) by as much as 300%.
Think of a tub of butter. If you lightly rub your hand over it, than you barely remove any of the surface. However if you dig in aggressively and really claw at it you could remove 1/2 the material in one shot. The product (hand) was the same, but the method was different.
If you are careful and your swirl marks are not do to deep, you should have no problem using M205 many many times with out affecting the life of the clear coat. However if you attack your paint like the Hulk, than even a fine polish like M205 is going to wear it thin after a while.
