There's NO official lifetime membership ie if you buy Pro from the official site. Some scam sites do offer a 'lifetime membership'.
You don't have to update an official version either, the purchaser can use the version(s) they've bought for as long as they like.
Updating isn't going to prevent viruses...it's up to the user to make sure they're scanning files after download with their AV & to be aware of what file types are easily infected, whether file size looks correct etc & learn what to avoid