I have 12 Mobil 1 filters for my 2018 Jeep. I normally don't stash that many, but they were $4 on clearance. I bought them at 3 different Walmart locations and left 4 or 5 on the shelf each time, trying to give others a shot at them.
I probably have 1 or 2 Fram Ultras for my 08 Jeep, one Ford Motorcraft for the 2015 van, one Ultra for the same van, and one Ultra for the 04 Grand Cherokee. I normally try to keep at least one, and since they are good for 20k miles, I think one is enough. I don't run them that far, but knowing I could eases the need to keep more in the stash.
I will probably settle ultimately on two for each vehicle, most likely Fram Ultras, unless I find a deal on another premium filter.
I have built up a bit of an oil stash, too, with 10 quarts of Rotella Gas Truck 5w20 and 18 quarts (6 quart boxes) of Havoline Pro DS 0w20. I'll probably load up on more Havoline, since it is priced well and the boxes stack easily.
Today's prices (sometimes with rebates) on good oil and filters makes it a great time to build up a stash.