I think there is adequate evidence to say some classes are built to only actually function properly when there is down time. As in they were designed with fallow periods being an assumed thing. That being said there is only down time when it makes sense that there could be and when the pcs actually go about making sure they are having it.
How long do they plan on being underwater and away from the Wizard? The spell lasts 24hrs and can be cast on 10 people. Making potions and rings are literally a waste of time and resources.
Ummm...no...if its a highly aquatic campaign making rings is definitely the best option only surpassed by making a back up ring for each person. This is also made even more worth it (though its already worth it even without the following) if your dm is one of the ones who believes that moderate thought bottle use is permissable.
IDK where you learned math, but spending hundreds of thousands of gold to make two rings for each player is a smarter use of resources than casting 1 3rd level spell slot a day. They even have a druid for back up. It would cost them less to horde components to cast Raise Dead on the Wizard everyday. Not only that, but the spell can be ritually cast, so it doesn't even have to take a spell slot. The only time when you would need a magic item or potion is, when the GROUP has NO ONE who can cast that spell at all. They have 2 people who can cast it as a ritual and only need it cast once a day for the whole party.
