Mine is 10%. When I was calling references, one lady said her bank made them adjust it to 30% and that is the only reason she thought they finished. We are wrapping up the project within the next 2 months, so ask me then.
My advice is to spell out what needs to be done at each milestone. It will say "framing" : OK, what exactly does that mean?
Also ask to see receipts or confirmation for all big items that you pay up front like cabinets. We had an issue where things were not ordered, and it set us back months.
That last payment should be a large enough percentage to incentivise the contractor to complete the job, with the final punch list complete and to your "reasonable" satisfaction.
The final payment was very low (a couple thousand), and others were huge, but based on paying for materials, cabinets for example (large kitchen + 3 bathrooms). We were not able to negotiate, as the draws were (mostly) based on their costs for ordering (plus lots of mark up I'm sure)
If you've done some type of remodel, what % was the final payment? We are beginning a project and talking to contractors. Trying to get a sense of how payments should be scheduled. Also, if the set final amount is a very low percentage, can you negotiate?