Interestingly, I also recently noticed that we are using around 75% of the allocated space on each of our buckets even though they have been up for 7.5 months. For us that's still more than enough space so I'm not worried about it.
If it helps at all we're using an older version of memcached, 1.4.1, each bucket is 1GB and has about 740MB of that used. A lot of stuff we set gets deleted or expired, but there are plenty of things that get set with no expiration. You'd expect the buckets to fill up eventually... Here are stats from one of the buckets: STAT pid 3746 STAT uptime 19995681 STAT time 1271735741 STAT version 1.4.1 STAT pointer_size 64 STAT rusage_user 20656.508733 STAT rusage_system 33432.810440 STAT curr_connections 849 STAT total_connections 40910273 STAT connection_structures 4494 STAT cmd_get 1134194114 STAT cmd_set 415640237 STAT cmd_flush 0 STAT get_hits 428039413 STAT get_misses 706154701 STAT delete_misses 530392232 STAT delete_hits 136872073 STAT incr_misses 23286903 STAT incr_hits 101619485 STAT decr_misses 502 STAT decr_hits 4139 STAT cas_misses 0 STAT cas_hits 0 STAT cas_badval 0 STAT bytes_read 539287620767 STAT bytes_written 581614893372 STAT limit_maxbytes 1073741824 STAT accepting_conns 1 STAT listen_disabled_num 0 STAT threads 5 STAT conn_yields 0 STAT bytes 774883798 STAT curr_items 1132112 STAT total_items 350437440 STAT evictions 52738486 (note: our hit rate isn't so good but it's a bit misleading; the way we use memcache, sometimes a miss tells us all we need to know and doesn't result in a set) -- Subscription settings: http://groups.google.com/group/memcached/subscribe?hl=en
