if a user gets banned is there any possibility of such user to recover their accounts after some years or are there programs organized by forum moderators that can help users recover banned accounts.
You meant permanent ban, not temporary ban. Then, the ban is permanent and the account is banned forever. It can be appealed for as jackg commented, if not unbanned after appeal, then the account is banned forever.
But it's stressful growing an account from scratch to a high profiled account only to get banned permanently without any form of future consideration.
People can appeal, but best to avoid ban from the onset after account registration. There are some people that go against the rules and given temporary ban, there are cases of appeal and unbanning of account. But prevention is better than cure.
I don't think permenant bans are done lightly though and they can be appealed if they seem inaccurate.
Although, the chance that admin or moderator will unban a banned account is very slim, but very possible someone can appeal and be considered.