I have a friend who runs a small drug discovery company and has a proper lab. He can mix me up whatever developer I want using magnetic stirrers etc, from bulk chemicals, which will make some developers very cheap for me.

I have 3 x 70mm backs for my blad, and 500ft of Double-X Aerial film and 600ft of Plus-X Aerial film. I havn't got my 70mm reels yet, so I havn't had a chance to play. However, I will need new tanks as I've just got a tiny 35mm paterson tank.

Since the film is high contrast and old style (1969 formulation) Kodak, I'm thinking Diafine is going to do a good job of this. My plan is to use 7 or 15 litre Kodak style square tubs (3F or 7F), and lower my reels and sheets on racks into this. Since I've read that Diafine basically lasts forever, and my chemical costs are cheap, I was thinking just to leave these 15L tubs filled with Part A, Part B and Fixer. Even maybe putting in 3 deep tanks (82cm) as part of the sink.

However, my question is, how long do these chemicals keep and do they need vacuum sealing to keep. Or will just the lids on top suffice?