I have over 18 claims that Shimano has taken care of through the shop I work at and out of them none showed any problems and all came off bikes that were being used until other problems took the bike down. There are no hills in our area so cranks under warranty don't break much here. I would ride the bike in a flat area and try to avoid standing up pedaling, ride it like a cruiser and you will be fine till you can get the warranty replacement

Glenn