I'd have to agree with this, some form of cooldown on votes where they expire after a set term to ensure people are constantly aware of who they're voting for and ensuring these witnesses are holding their end of the bargain not just 'getting by'.

There are many 'new' witnesses that come and leave because they can't actually make enough to even cover costs. Whilst it should never be about 'making a profit' there needs to be some system to ensure the witnesses and voters are 'active' enough to contribute to the network.