Thanks for this discussion, everyone. At least I know I'm doing the right thing by optimizing it often. :)

Much quieter site. Size of the database 12 MB; this year (average daily use):
211 unique visitors, 15 simultaneous connections, 761 visits, 1090 pages, 2815 hits, bandwith 6.28 MB.

For comparison: size of the database is 156 MB, 219,675 unique visitors, 881,148 visits, and 730 pages.