Considering LLL.com's are getting pricier daily, an L-L-L.com might be an attractive alternative.
I personally own about a hundred of them. Was that a smart buy or am I a sucker? We'll found out in about a year or 2
Do you mean a domain name with a letter repeated three times? I guess not, there would only be 26 of them. Or any three-letter domain name? Or domain names with a word repeated three times? Uh, there would be more than 17,576. Or with a word from a particular class of words repeated three times? Something else? Do, we have a mathematician that can work this out?
For the few exceptions, though, I think the dashed version is a poor substitute for the genuine article - as with all domain names containing dashes. (When I say the "genuine article", I am referring to the fact that the public expects domain names to not contain dashes.)
Problem with that is they may well get the domain from you without payment to you (but certainly not without cost) through a WIPO action.
I'm not sure that the fact that you've systematically registered a bunch of these necessarily protects you. Perhaps even the contrary. They may be able to prove that there's little other use for these names, and that you must have intended to sell them to companies that have these names.