Interesting subject!
Here in Canada there is no minimum hourly requirement when to go solo.
At my former school (Canadian Helicopters) most of the guys went solo between 20 to 25 hrs. Everybody had to successfully complete part of the flight training syllabus including full on autorotations.
Later when I became an instructor myself most full time students would still solo at about 25 hrs. The big exception was a part timer who soloed at 85 hrs.
I totally agree with some guys who say that when going solo is not a big deal.
I have also seen so many times that someone who learns slower initially will make a better pilot later.