Is z-address reuse considered good practice and, if so, when might one want multiple z-address?
In the zcash blog post Anatomy of a zcash transaction, Paige Peterson notes:
Thankfully, when sending ZEC from a shielded address, that data is kept private so sending change back to the sending address is permissible. In Zcash, all transactions between shielded addresses look identical so the reuse of shielded addresses is not vulnerable in the same way that transparent addresses are.
This suggests that reusing z-addresses is fine but also that there are no consequences beyond privacy. I've found no explicit guidance.