You can't do titers for rabies - rabies is given by law - either every year in some states, or every 3 yrs like here in AZ.
For distemper/parvo, I do not in any way feel titers are worth the $ - remember, they don't really tell you anything since they only can indicate humoral immunity ONLY -- they tell you absolutely nothing about cellular immunity.
Also remember this: you can have a negative titer, but actually *have* cellular immunity and be able to fight the disease; you can also have a positive titer, but have NO cellular immunity whatsoever.
Sooooo...see why they're not worth it now
...?!!!