Kindle Touch SO switching accounts

[hadxs]

Hello, I'm new to this forum but i have been a Kindle user since the 2nd Gen. I have a question that I could not find an answer to, so I was hoping you could help me a little:

I live in a country where the kindle is not officially available so all my readers have come from craiglist-type sites, anyway I find the ads on the Special Offers models quite annoying so my question is: If I pay the 40 USD necessary for "upgrading" my Kindle Touch SO to an ad-free state . . . will that only work with the account in which I pay for it or will it work normally no matter to which account I sign in?  For example, I pay the upgrade with the ACCOUNT #1 (Mine) but after a while a lend my kindle to a friend (wich is also annoyed by the ads) that resets the kindle and signs in with ACCOUNT #2 (Friend), is he going to have ads or does upgrading in one account "unlocks" the kindle no matter who uses it?

Thank you for any help you could give me and sorry for my awful english, is a little odd for me writing in another language.

[koland]

Only on your account.