Also in my experience with Potassium Oxalate the age of the developer affects color.
With a brand new batch of developer heated and using Palladium I get pretty warm prints. After a couple years seasoning with Pt/Pd mixtures it won't change color much regardless of temp.
Dennis, with old well-used developer, does the development temp still affect the "speed" of the paper (ie, increase temp -- decrease exposure time under the UV) ?
At least with LF landscape, a bad day of photography can be a good day of exercise.