I can offer a single data point for D76. I use D76 as a one shot. Last week I used the last of some three month old stock. I developed an HP5 test sheet (exposed thru a step tablet) in 1+3 at 68.0 F for 9 min. The HP5 test sheet yielded CI = 0.35. I got CI = 0.33 under the same conditions with fresh stock two days later. I don't have an extensive data set, but the CI with the new stock looks consistent with the last test sheets I developed with fresh stock. CI changes 0.020 per minute the way I process and I don't usually miss a target CI by more than 0.01, so I'm inclined to believe the observed difference was due to the developer not in how I was processing the sheets (hand agitated Jobo tank).