I've been using Ilford DD-X (1:4) with Kentmere 400 as I get back into the world of film, but I didn't have a ton of experience with all of this years ago. I usually develop two rolls of 35mm in a stainless tank, and then throw out that batch of developer. But occasionally I'll shoot a roll of 120 or some other type of 35mm b&w.
I have re-used the developer for a third roll of 35mm done right after the first two and everything worked fine. Right now I've got two rolls of Tri-X 35mm, one Foma 400 120 and an HP5+ 120, so I'll develop them in three batches in a two-reel tank. Can I use the same 1:4 batch of DD-X for all four rolls developed all in the same day (so storage times aren't relevant)? I have read about increasing development time 10% for additional rolls but I'm wondering if that's a myth or solid advice. I do have some old powder D-76 included with a box of darkroom stuff bought recently, so I'm wondering how this works for other developers too. Yes, I'm an admitted cheapskate...