If that works for you, then stick with it. I've used up to 25% protein for rats with absolutely no problems, with better weight gain than with a lower protein content, and with no problems for my males. I was producing stockier babies at 20% than I was with a lower protein content. However, I don't plan on breeding my females until they can breed no longer. I have never bred a female to the point that she could not produce anymore, I simply have no reason to, and would rather retire my females early with less litters. Granted, I have 4 balls and one corn snake, and the rats come as pets first. I have the luxury of retiring females without burning them out.
If what you do/use works for you, then stick with it, but I'm going to stick with what I know and have done in the past and know to work.