Michael, although Shimano advices you to buy a new pin, its possible to use the old one.
I used my chain for a year now, one time broken and fixed with the same rivet, no problems dispite my brutal shifting

I know when you push the pin through, the little edges on the end will brake, this should be a weak link.
But if you do the job well and get the same rivet ends on each side of the link, i see no real problem.

What is your opinion?