For about the last year, the site update process has archived the previous state of TM as part of each update. I had pretty much forgotten it was keeping things for so long. It takes a lot of storage (about 357 GB at the moment) but the server has no shortage of disk space at this point, so I plan to keep saving things. So if you ever want to have access to an old log file, old stats about the contents of a highway system, etc., you can send along a request by email to me or in a PM here on the forum. Saved for each site update are the .sql file used to populate the DB, and the contents of the graphdata, lots, nmp_merged, and stats directories.
Also from these archives, tools like "grep" can easily generate fun output like one attached which shows my overall stats in active+preview systems over the last year. Nice to see I've had a productive year, adding 3000 miles between new travels and previous travels on systems that have reached preview or active status in TM.