How much recovery time would you say must be allowed between training sessions?

It all depends on your body's ability to recover, it varies differently from person to person and how hard you train in a session, the general rule of thumb is a day between sessions.

thumb i concur.

it all depend how hard you train ..
i am training twice a week now so i get some good rest between training sessions...

I have never trained the same muscle groups two days in a row, regardless of my chosen discipline. I've asked the question because there seem to be those in the sport of A.W. who train in this manner.

Training my wrists every second day at the moment and there are feeling stronger for it. Never train back to back days though.