They are able to gain experience much the same as you do. The true
difference is that they chose not to gain it by killing others, and
infact probably only gain it when they kill in self defence. Of course
with the number of people killing them all the time, it is little
wonder they never keep their gains.

Isildur.

Penned by my hand on the 12th of Mayan, in the year 243 AF.