I know you can't attune to 2 items of the same name. This question is more about the other effect of Rod of the Pact Keeper that lets you restore a spell slot once per long rest. If I have 2 Rods of the Pact Keeper, could I cast 2 buff spells, use my Rod of the Pact Keeper to recover a spell slot, then during our short rest switch attunement to the other Rod of the Pact Keeper and get to use that one's spell restore option as well? So if I managed to have many rod of the pact keepers, I could effectively make the mechanic 1/sr up to as many rods as I have.
You must spend a short rest to unattune.
The rules for attunement state:
A creature can also voluntarily end attunement by spending another short rest focused on the item
So you need to spend a short rest to unattune, then another to attune to the second rod.
If you have enough short rests in the day, ask your DM.
The tricky thing here is the long rest limit condition:
You can’t use this property again until you finish a long rest.
We could interpret this to mean you cannot use this property of this particular rod until you finish a long rest. Alternatively, we could understand this property to be rod-agnostic, that is, if you have two rods "this property" of each rod is the same property, so it can only be used once, no matter how many rods you have. This is going to be up to the DM that gave you two Rods of the Pact Keeper.