I wouldn't say "perfect" because that's a bit of a stretch ... but .. a couple of times now I've been lucky to have good enough alignment that I don't need any other polar alignment done and be able to take 10 min exposures OK at 500mm focal length.
It is very rare but your chances are significantly increased by having a process you follow to get that initial setup right, knowing deviation from magnetic south & using a compass, leveling the mount well, setting latitude best you can.
In the early 80's when ASNSW had a concrete slab at Mt Bowen, I had three marks on the concrete and was routinely able to set up a C8 roughly aligned on to the pole, straight out of the car; usually it was within 1 or 2 degrees and easily corrected from there - and it was routinely good enough for 10 min shots with a 500mm lens.
Repeatable setups should be possible if you have a regular observing spot on a solid surface, and the mount mechanically will preserve the alt/az adjustments despite being repeatedly disassembled/reassembled. Some mounts will, some won't.
I'm also tempted to put some small holes in the stone at my regular haunt, for the same reason.
Only refined occasionally because of pesky rugrats bumping
the scope or ground movement.
If you're dreaming of doing it I say don't hesitate. You will
wish you did it years ago.
. 
