Auto voting to optimise returns is all very well, but it does not really take account of post quality. Whether the cutoff is 5 minutes or 15 is irrelevant unless you are on here 24/7 to catch new posts at the right time. An issue with strategic voting is that it can mean the same people keep getting the good rewards as they have good history, i.e. self-perpetuating benefits. I know good curation projects have people looking out for quality content. I will keep most of my voting manual and accept that my rewards will not be optimal. I do some auto-voting on some small accounts to try and build them up. I have the @tenkminnows account working on this and may tweak when it votes to help it build up more SP. I know it gets a better curation return than my own account.
I have never been into buying votes apart from a few experiments. I would hope that the free downvotes will be used to balance out rewards a bit better.The reward curve that is expected to give lower rewards to most people is putting people off. It still needs to be about quality though.
Cheers