Probable memory eating for Memcached storage

[alpha-and-omega]

I am talking about Memcached storage implementation (probably other too).
Since you use memcached::set with ttl = 0, old unused buckets will stay in memory forever, and this is not good for websites with bucket-per-ip. For websites with 100000 visitors per day it will eat >100 bytes per record = 10Megabytes, and will grow each day. In a month it will eat ~ 300Megabytes and some vps servers will go down.
I think it should be possible to set ttl to specific reasonable value.