If a feature is implemented, the vote is made available again. We do limit votes so that each vote made is meaningful (e.g. someone isn’t just voting for everything and anything). That doesn’t stop you from adding a comment and showing your support for that request in another way, however.
I can’t comment on the difficulty of implementing a feature unfortunately, as I’m not part of the development team. But please, rest assured, that each feature request is assessed on it’s own merits and the situation surrounding it.
Can you clarify what you mean here please? We can certainly investigate this if something isn’t working, but it may be best to start a #bug or #support thread for that separately, so this feature request thread remains focused on that.