2 sets of rebreather cylinders, yes. I actually want 3 sets.
Easy enough to do a day of diving on one set. The second set of for a weekend of diving. I often keep one setup as a shallow and the other as deep diving.
I'm looking at a 3rd set as I have done 3-day weekends and that 3rd day I find myself blowing through a tank of air in the parking lot to drive the booster to get that 3rd fill. Not in a hurry, long term goal. Not anything I can't work around. But I would rather work (around) less when on vacation.
When you are setting up your bailouts, make sure you have fresh hydros. After you blow through them in training and refill them again you won't use that gas for a long time. There is a bit of truth to the jokes about the bailout cylinders several years out of VIS and a couple years out of hydro. Eventually you should practice doing a bailout just to empty the tanks and update the stickers and stampings.
Not sure how they will teach cell replacement. I go with the rotation method. That is replace one at a time a few months apart. That way a bad batch won't show up winning the voting logic, just 1 bad cell. With that said I just keep the oldest cell or two. They are still in spec, just toward the end of the useful life. Those are in the save a dive kit. That will be a better plan then keeping new cells in the spares. They age out regardless if you are using them or not. A year old used cell that was working good when you took it out is a better spare than a brand new cell that is a couple years old.
Go with what the instructor teaches for now. Once through that you can make personal adaptions.
Don't be in a hurry for that tech100 class. There is a huge reset being put on your diving skills when you start the rebreather.
Say you have a 3 hour cartridge and have done a 2 hour dive today. Tomorrow you have a 2 hour deep and a 1 hour reef dive. With the spare I can use the first one for the reef dive and use the second fresh one for the deep dive. Hopefully that make sense.
