I have flown many times from the right hand seat with two of my mates who have tens of thousands of hours between them.
I have definatley learnt more from them than I would ever learn from a school, obviously some good things and some bad things. However unless I have agreed before the flight then I have not logged the hours as everyone else has stated it is not a mutlicrew aircraft.
The most valuable things I have learnt from them is bad weather flying and short rough strip operation with unlikely bush planes.
My advise to you is take the right hand seat option as often as you can get it, and learn from it. Forget about the hours, they will come in time.