You can cruise all day at 1250 and not hurt a thing other then your pocket book from the fuel going out the tail pipe. Drag racing, pulling and on the dyno you are looking at EGT's over 1600 for 10-15 seconds with no damage, no worries.
If your cruising around at 600 and go to make a pass 1600 is fine for 15-20 seconds. You have to heat soak the pistons to do any damage.