So, After a several year hiatus from analog photography, I'm starting up my darkroom again. I used to use the Kodak RA-4 chemistry one shot kits for home use. Of course, these are no longer available, so I'll have to use a replenishing developer. I generally mix smaller package size quantities and store the remaining concentrates in smaller bottles with no air space. This has worked well for me in the past. I was planning to use Ektacolor RA Developer Replenisher RT 10L , however I also noticed there Adorama also offers Kodak RA Prime SP Paper Developer Replenisher 10L which has a single concentrate instead of 3. It is more expensive than RA-RT. However, the single concentrate makes for easier mixing. So my question is does anyone know how the shelf life of the Prime SP concentrate compares to the RA-RT concentrate?