Agreed - total waste of time.
AFAIK, standard primers use a majority composition of Lead Styphnate - extremely stable stuff.
The "lead free" primers are usually DDNP (diazodinitrophenol), which is also pretty stable stuff. Slightly less so than Lead Styphnate, but that won't matter unless you're storing them in the open during monsoon season in Burma.
Military corrosive primers usually had Potassium Chlorate or Perchlorate as part of the mixes, which is why they are corrosive - the decomposition products of these primers include Potassium Chloride, which is quite hygroscopic and therefore draws moisture to the steel on which it deposits. The atmospheric moisture and the salt residue work together to rust the metal, just as dropping a nail in a solution of table salt would - substituting Potassium for Sodium, of course. No matter - the Chloride is the problem.
I would be concerned about storing non-loaded corrosive-type primers unsealed for long periods; both KClO3 and KClO4 are quite hygroscopic themselves. However, with military crimped or lacquered (or both) ammunition, the system is already sealed on a per-round basis.
So, in short, it's not going to HURT anything to vac-bag 'em... and if I were burying them I'd definitely waterproof the lot quite hardily... but if they're going to be stored in the garage or shed? More trouble than it's worth, for my money.
-M