A: 

Hi! I am also interested in the possibility of turning the phone discoverability for the infinite time. However the app I am thinking of is not intended to work in the tiny closed environment only and I would like to make as few requirements for the potential user as possible. So is there any chance to allow infinite discoverability or to let the app to enable it without disturbing the user in the future API or I will have to give up with this app on Android.

Sebo.PL
I think this would be best suited as a comment rather than an answer. Nevertheless, it may be something that is introduced in a future API; the issue is listed as an enhancement with medium priority on the Android issue tracker (http://code.google.com/p/android/issues/detail?id=6348). If you care about the issue, I'd suggest starring that ticket and posting a comment.Right now, no, there is no way to do this from the API, and it is proving difficult to do it otherwise...
kanov-baekonfat