20 races is the maximum really that I feel should be in a season. Ross Brawn is right in that it's pushing the boundaries of what the teams can be expected to do, and what their staff are expected to endure. They'll basically have little or no break between now and end of the year. Then they start straight back into it with development of the new car. Too much.
I understand Brawn's issues, but in terms of a racing series, F1 has always had room to grow in terms of its schedule length and although he complains, he probably would like the additional revenue and additional opportunities to gain more points. Sadly those who will struggle most ni a longer schedule would be the HRT, Lotus and Virgin teams.