Repackaging bulk seeds

What seeds are they?

Winter squash, pak choi, French beans.

When you say airtight tin DD do you mean like  Tupperware container or is that no good cos its plastic?

Doesn't matter what it's made of, if what you're storing is dry, as long it's airtight. You get problems if you try and store self-save seeds that are slightly damp.

I'd probably be more correct in saying I store in a nearly airtight container. It's a PG tips tin!

I've seed in there that are about 7 years past their sow by date that are still giving me nearly 100% germination.

I really don't think you need to go to such lengths as vacuum packing. The seeds you buy in the first instant aren't.

I'd go with the metal tin. Not only will it keep the seeds drier but it will stop rodent grazing which is worse than rotten germination.

lots of me are in reused envelopes in old ice cream tubs

i`m inclined to think the temp has more of an effect anyway, ive bought seed from the seed sale that have been in the centrally heated garden centre all year and hardly any of them have germinated!
i just keep mine in my tin in the shed and they seem to fine.