Rules for Old Timer HOF Committee

[GehrigFan]

I was looking through my cards and came across one that I have always liked because he's a common, but his stats are HOF caliber... an 1887 Buchner Gold Coin Jimmy Ryan. I know he has been mentioned before on the board, as his stats are far superior to tons of people in the HOF currently, but he was a crotchety old guy that got in a lot of fights which doesn't help his case. Some stats = .308 average, 2513 hits, 1093 RBI, 419 SB, 1643 Runs, etc.

But my question is actually regarding what the rules are for guys like this. Are they eligible indefinitely, or are there only a certain number of years they can be voted in by the Old Timer Committee before they drop off and are ineligible? How often do 19th century players ever get voted in now, say in the last 20 years or so, or does it really not happen if they went this long without getting in?