I've enabled the Hibernate query cache. And I've discovered that by using Criteria queries of "natural ID"s solely, there is little reason to replicate the timestamp cache; especially when using clustering.
I added a property setting disables the timestamp cache entirely. What happens in cases where a non-"natural ID" query is made is that the query simply occurs without caching at all, so this works fine.
This is a patch, applied against Hibernate 3.3 branch which allows for timestamp caching to be disabled, i.e., by setting: