##The best of the bunch...##

**Mouse Guard:** You have to have Level in successes, and Level-1 failures, in significant uses of a skill to have it go up. There is a limit of 24 skills per character (of a list of 50+).

**MegaTraveller:** Unlike early editions of Classic, it has both in-play experience (use the skill enough, it goes up, but you can only gain a particular skill so fast... and it also has the Int+Edu limit, where if your total of those two stats is the limit to the number of skill levels you may possess; if you exceed that with a new level gained, you must reduce another.

**Classic Traveller** in later revisions of the second edition, namely **The Traveller Book** and **Starter Traveller**, and in **Book 7: Merchant Prince**, the Int+Edu limit is applied at the end of mustering out. It is from these sources that MegaTraveller gets that rule. *The 1st Edition (1977-1980 printings) and 2nd Edition (1981 and later printings of Books 1-3) of CT do not include the Int+Edu limit.*

##A few that other people think do, but I disagree, and why:##

**Classic Traveller:** There is almost no skill gain in play; it takes characters years to acquire a skill by study, and years out of play to acquire one by taking a sabbatical. There is an upper limit on skills based upon the sum of Intelligence + Education, starting with certain later supplements; it's not in the little black books versions of the core rules.

**Burning Wheel:** At least in Revised, the skill loss rules have been deleted... Luke's commented on so doing. The rest of it, however, isn't bad, tho' in-play skill gains don't mirror in character generation. The lifepaths are a source of both inspiration and drama, but I'd not call them realistic.

*SevenSidedDie notes that the original Burning Wheel rules included skill loss rules, and that those may be ported to Revised.*

**GURPS:** While GURPS 3E has some wonderful practice requirement rules, it has no skill acquisition process in the first place. There is the official statement that 1 point = 250 hours of practice...

##Skill loss Rules? Are they important?##

You'll note my reasons for BW are the lack/loss of skill loss rules. Doesn't make it any less of a great game (in fact, I'm in a skype game of BW) but it does make it less realistic. I've personally lost a number of skills from lack of use, and many characters probably should have...