Buy what you like and take care of it
It is true that brass frames are less forgiving of abuse than steel frames. Abuse in this context means shooting "heavy" loads, frequently, combined with poor maintenance.
There is no need to shoot maximum or over maximum loads in any BP weapon. They are all more accurate at moderate loads, so if one tries to do the best he can, the brass frame should live as long as the steel frame.
Personally I don't like too much brass - the grip frame is usually about all I can accept in a CP revolver. But,
But, if the brass frame lights your passion, by all means go for it. The idea is to enjoy yourself. Just remember to take care of it. You don't need to baby it, just use common sense and treat it like it was meant to be treated, just like all the rest of us.