Actually, Thumb is based on Testing so better keep Testing enabled. You can keep Stable enabled too if you wish but there is little point since everything that is there is also in Testing at the same or newer version. Keeping both will unnecessarily extend update times.

That is correct. The KEYEXPIRED messages mean exactly that, keys expired for Nokia repositories. Nokia is not going to renew them so the only thing you can do about it is ignore them. Just proceed to install the updates without verification. If those are the only warnings you see, then it is OK.

Mods: I really wish there was some info about this printed in big friendly letters on the front page. I get tired of repeating the same thing over and over again. Can something be done about it?