For how long would you need to stare into a laser pointer to lose your vision?

Depends. Don't try this. Laser pointers even with low mw energy produce a concentrated beam of light further focused by your eye. This can permanently burn a spot on your retina. Ophthalmologists have seen damage with even the weakest laser pointers . These are not toys. A there are more high powered lasers which will do the burn in a hurry.