list archives (/ Thunderbird question)

Are list messages being actively archived and put online anywhere these days? I have a shade over 68,000 messages in my classiccmp folder, going back to 2008, and Thunderbird is about ready to explode. I need to have a clear-out; can I delete them because they're available somewhere, or am I better off keeping a snapshot of what I have? I'm sure other people have offline copies too, but I'm more interested in them being immediately accessible should I want to refer back to something I know I've seen in the past. If I remember right, the archives on classiccmp.org itself have always been a bit patchy. (Thunderbird question: If it is sane for me to keep them, do I just need the 'classiccmp' file at ~300MB, or do I also need the 'classiccmp.msf' file at ~36MB? I'm not sure if the latter's perhaps just an index which will get regenerated in its absence anyway?) thanks Jules