Not if you buy them today to use later I would think. Since you gave up the $$$ today, it won’t do anything for you anymore even if you don’t buy another stamp again I’d think. Compared to buying a stamp whenever you need one in the future but not tying your cash up until that moment.
Over the past 5 years, they've beaten:
* VT stock (total world index fund)
* US I-Bonds (inflation-indexed bonds)
* Fed rate for T-Bills / any HYSA
* Any other bonds