Sure, but with a system that is active (like HN), there would be enough votes coming in frequently enough to handle the ranking updates and account for time increases without needing to hit the system every 5 minutes.
I think a hybrid system would actually best. Otherwise posts that don't get many votes wouldn't update their score.
The best would probably actively update on votes and do a catchall operation on ones that haven't been voted on or all on a certain periodic cycle.
Also, if only updated periodically, the front page would "skip" so to speak every X minutes (exaggerated changes in rank), whereas re-scoring on each vote would allow smoother changes in rank.