here you go...
First of all, you won't get renewed unless 90 days or less from the expiration. So if you are outside the 90 days, the application will be held until 90 days and then submitted.
Submittal occurs immediately, and my last renewal showed up in the database on the 89th day before expiration; I submitted about 100 days out. So start checking the database then. (Recent database problems at the FCC and subsequently QRZ.com don't supposedly affect renewals, and only affect new licensees.) Once it shows up in the database you should get the paper in about 7 days or so; mine showed up in 4 days, but we are in the mid-west, I'd suspect it could be a bit shorter or longer depending on weekend/holidays and distance. You are at the mercy of snail mail; and of course that assumes there was no problem with any questions you answered or info you supplied.
The renewal is effective from the day that it occurs, but the new expiration is based on 10 years from the old expiration date. So if it is Feb 29, 2012, and the license expires on May 28, 2012; the new license won't expire until May 28, 2022.
Hope that got all your questions.