This is something many of my mates used to try back in the old goldbox second ed AD&D games. A sort of survival of the unwilling fittest.
Whilst being fun for awhile, I avoided it after being punished for a marathon session in Silver Blades. I recall that after obtaining enough xp to level up three times, I only gained the one as the xp levels of my characters rounded back to just 1 xp point over the level just gained.
So yeah, its not an action I normally reccomend in AD&D games unless you really are just experimenting or in denial of your own experience.