What this shows is that since the subtracted term, τ (1- Pvalid), is strictly positive, the miner's expectation of revenue, , is maximized if the time to verify the previous block is minimized (i.e., if τ is as small as possible).
Actually, is also maximized if Pvalid == 1 (or Pvalid as close as possible to 1).How to reach this result ? My humble proposal: make a deal with a few mining pools. Participants will never push invalid blocks to others participants. Blocks received from the cartel aren't checked before hashing a new block.
Conclusion: As the average blocksize gets larger, the time to verify the previous block also gets larger. This means that miners will be motivated to improve how quickly their nodes can perform the ECDSA operations needed to verify blocks or that they will be more motivated to trick the system.
EDIT:
Quote from: Peter R
Am I being sensitive or is this an unnecessarily spiteful reply from Greg Maxwell?
Well, he seems a bit upset for now 
but I think his message is close from what I've tried to suggest with my comment. We must analyze all the possibilities before jumping to a conclusion which backs our initial hypothesis. The point is valid for all of us, whatever our opinion on this blocksize issue.