To tack onto Nando's suggestions, also consider purchasing either RMGI's LPR-35 (1800 ft/1mil thick) or SM-911 (1200 ft/1.5 mil thick) if you find sourcing NOS tapes to get too expensive once Freddy runs out. Splicit.com has 7" reels of LPR for $27.50 and SM-911 for $22.95, which are pretty reasonable compared to prices for sealed Maxell and such on fleabay.
I personally stick to buying new tape for a couple of reasons, including supporting the tape manufacturers - who, if they go out of business will leave us in a real lurch - and I don't like being unsure of the storage conditions for tapes from 40 years ago - no matter if they are sealed or not. And used tape, well, that's just a total crapshoot unless you personally know the person from whom you're buying.
Just my .02.