I think that making reputation temporary will increase constant participation, since the reputation will slowly decrease if they do not participate and gain more reputation. I thought of two ways to do this: deterioration and expiration.
Deterioration is basically taking a certain amount or fraction of your reputation away after a period of inactivity. Some examples of rules would be like taking away 5 rep. per every 30 days of inactivity or 5% of your rep. for every 45 days of inactivity. This would force you to be active so you would not lose rep.
Expiration is basically when reputation (specifically from upvoting) expires at a certain date after retrieval. It is not based on inactivity. The idea is that you gain reputation about everyday to keep it at a stable level. Deterioration and expiration can be combined so only a certain part of the total rep. gained will expire.
The Questions at Hand
Is the constant decreasing of reputation a good idea? Even if the answer to the previous question is wrong, would deterioration or expiration be better? What rules would be used? And in addition to all those questions, why so?
Note: I thought of specifically applying this to voting only.