This wins about 4s over a 54s real-world benchmark.

s/illegar/illegal/g

this implementatian is much more verbose but faster, especilally if you are dealing a lot with JIDs
on my box, ./testall.py now takes 45s. It takes 53s in the old implementation (about 15% faster)

Passing cache_lock=True to JID() will insert the JID into the cache
and prevent it from being dropped from the cache.