Voted for
- No, witness voting is perfect as it is.
I have given thought to witness vote expiration and anything short of 1 year I don't think is good. I'm not sure any time would be good.
If witness votes started expiring, Steem would be a non-stop campaign system for witnesses. As it is, most users don't vote for witnesses, most users don't for witnesses based on actions or competence. I would consider some expiration after a year though.