If the lender tells you it will be safe to remove the loan contingency after 18 days, but then it ends up really being 25 days, that can screw up your entire deal.
The seller might not grant the extension and escrow could be canceled!
This is why it is so important to work with a lender you know and trust.
If the lender gives you a certain amount of days for a contingency, then they should stick to those days!