Thats a controversial subject, I've heard that polishing once a year for 20 years would still not remove enough clear coat to wear thru to the paint if using a fine machine polish...using something like a #2 or #1 machine polish would probably shorten that. Technique would play a role, someone not knowing what their doing could bear down too hard using an orbital(non-random action), or do it too often (once a month?) :dunno: I asked a detailer that was visiting Griots one day and spoke to him for an hour..he chuckled when I mentioned that wearing thru the clear coat with a random orbital...if you ever own one, you'll see what I mean, you can stop the pad easily with your hand, thus, you cannot bear down too much pressure on the pad or the random orbital action ceases.
High points on the "hips" of contours could potential wear thinner than straight flat area's, but again, that was a concern in the days of strictly orbital polishing. Random orbital prevents heat build up on these high spots.
I certainly wouldn't be real concerned with wearing out clear coat, unless you use a real cutter machine polish consistently, which you wouldn't need to do.
My 2 cents