Typically you will want to allow 5 days for the buyer to make full loan application and no more than 30 days for full loan approval. If your buyer is trying to close within 30 days you can request that it be sooner, but with current loan and appraisal regulations...unless you are dealing with a 20% down conventional loan it's taking the full 30 days right now.
Getting a financing contingency removed is trickier. It's typical to have these set at 28 days, however, these contingencies continue after the deadline, unless the buyer takes the action to remove it. The challenge for a buyer is that lenders will tell you that the loan is approved through underwriting, but they'll always have conditions tacked on -- like verification of employment and credit just before closing, etc. As a seller, to get any real protection from financing contingency contract language, you must complete a lot more due-diligence on the buyer's qualifications before you actually ratify.
That's a long answer, but I most sellers think that if they get past the number of days on financing, then they're home free. And that's simply not the case. The buyer can have ton's of exits out of a contract based on financing.
Hope that helps. Good luck.