When developing an app, I used to test it with a Development provisionning profile. But, this provisionning profile, as well as the distribution one, have an expiration date. Does it mean that :
any app I buy on the appstore may stop working if the developper does not renew its subscription to the Apple dev program, so he can't renew the provisionning profile ?
My own apps that I install on my won iPhone may stop working after a year if I don't renew that program ?
If yes, is there a way to make my own apps work "forever" on my iPhone even if I don't renew the Apple dev program ?
Any app purchased on the app store does not function off of a provisioning profile (the word "provisioning" should be the clue here).
A provisioning profile is necessary for any app installed using the binary that by pass the app store. For example, when loading an app onto your device for testing or sending out an app to beta testers, the app runs using a provisioning profile.
The reason that a profile expires within a year is because your license to develop expires annually unless renewed. Apple wants to ensure that you don't keep using your own apps on your own device unless you shell over their $99. So as long as you're conforming to Apple's rules, any profile will expire on or before the expiry date for your developer's license.