I've recently started mixing my own chemistry and am interested in mixing up a warm-tone developer which will complement the Dektol formula I'm currently using. I've been reviewing formulas in the Darkroom Cookbook but am having trouble picking one to start with. Any suggestions? One concern I have is lifespan, as I'm using a Nova slot processor and generally keep chemicals for 4 weeks. The Cookbook doesn't really speak to this issue, except for very short-lived formulas.