There is a discussion around destroying old value pools.
In particular, this section is interesting:
However, we’ve never established an expectation among our users about how long a pool will be supported before we pull the plug on dormant coins. Imagine someone buying some ZEC back in 2016, watching ZEC moon (as we know it will!) and then trying to dig up their old shielded wallet. Surprise!
@Daft Just in case, I would recommend checking in from time to time to see if there is an update.