I own (4) .TL Domains and yes when they are not re-registered they are dropped forever and not renewed, but if you keep the registration up to date you can re-register them and sell them whenever you want. I have no clue what some people on here are talking about when they say its illegal to register 1 letter/ digit domains. Most TLD's dont even have 1 letter or digit domains. If the do, they arent for general sale to the public without a hefty price tag.....check the domain news