Not all the cranks "climb" the spindle equally. Shimano gives specs for using their BB-s, which usually results in correct chainline without cranks being to far out, or hitting the frame.
However, you can sometimes go with a few mm +-. If you ride on the largest chainring most of the time, it's even better to have a slightly shorter spindle (as long as the FD can accomodate the shifting to the smallest chainring and the cranks don't hit the frame). That way chain will be straighter when used with mid-cassette cogs.

Also, some Shimano BB-s have a sort of a "stop" at the right hand side. If the crank bottoms out against that stop, before having gotten a proper preload against the spindle, you can expect the bolt to get loose over time, as well as the spindle to get damaged from "play" (even before you can sense it).