If I made some changes to my page to make my score go up. How long should I wait to know if the changes were effective?
See the AdWords FAQ thread. Q: How often does AdWords reevaluate my landing page? A: AdWords visits and evaluates advertiser landing pages on a regular basis.
I think that the update is every hour or so, this estimate mainly has to do with the painful wait it takes for the score to update consistently. I've seen a large change in the price I pay per click within an hour period. I'm unsure of the real time, but that is what I believe based on experience