Personally I do cancell ALL my rentals around 2 days before EOS, at the moment I'm putting them on for > 200% return in more cases!
Not to do so would be to throw around $100-$200 away.
Having said that it would be good to introduce some kind of 'rental lock system' - I'd quite happily rent some cards out for the longer term and lock them into a contract which I couldn't cancel for the period for the right price.
RE: You can trust my Splinterlands rentals..