It's worth pointing out that it doesn't really matter if somehow your SIM card should ever wear out, as long as you're on a contract or have your pay as you talk details registered. Just ring up your phone company and tell them your SIM is knackered (the call centre drone might take a bit of convincing) and they'll cancel your current SIM and send you a new one. Or walk into a shop, prove your SIM is knackered and they'll cancel your old one and give you a new one which should be active after an hour or so.

I used to run the phone and Blackberry contracts for my company and we had a box of blank SIMs that the phone company had given us. We did have to transfer SIMs for some people every now and then, and we'd just pull a blank out of the box, ring the phone company quote the phone number and old and new SIM numbers and they'd swap it over within an hour or so.

To be honest though we never had a SIM wear out, the times we had to change SIMs for people was either when they had an ancient SIM and were transferring to a 3G device (apparently your SIM needs to be a certain version, with a slightly expanded storage to work properly with 3G) or due to "mechanical failures" (one guy managed to leave his phone and SIM in an oven while it was warming up, another for some reason had his SIM out of his phone in a car park, dropped it and someone drove over it).

I do not know the exact figure, I only know that I have friends, who are using their SIM cards for well over 10 years now and it still works. The only problem I think that the metal contact parts that on the SIM card will get dirty over time, but this can be fixed by cleaning it.