robot skills

I could not find how a robots skill level could be increased beyond
4 either.  Just an idea: how about a year per skill level.

for example: the robot has 	pilot -4.   In five years, he will have
pilot 5.  This time could possibly be modified by intelligence and if
the robot was trying to increase more than one skill.

		any ideas...............

Also, is anyone out there interested in a PBM trillion credit squadron game.
- --Just anothrer idea.....