Updating console best Practices?

I'm looking for some conventional wisdom and best practices people use after upgrading the console software.

How many standard upgrades before doing a clean .iso install?

Do you just launch old shows, or do you make a new show then merge in old show info (as I've heard some people do)? What are the advantages of creating a new show then merging?

Anything else to be thinking of?

Thanks.
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