In a previous thread about this print developer, a concern came up about it's useful life and exhaustion rate. Since then I have a bit more input.
The last time I printed, I stored my partially used tray solution (diluted 1:11) in a green plastic soda bottle (figuring that a bottle capable of storing a carbonated beverage indefinitely must be pretty gas impermiable), with a poot of butane to displace the air in the bottle's headroom.
Tonight, after more than six weeks, I ran a strip through this developer and the image came up fine with a two minute developing time. I dumped this and mixed a fresh tray solution from my bottle of concentrate that I opened two months ago and stored in it's original bottle, again using butane. I ran another identical strip, for comparison, and it developed identically to the old tray solution.
Mike, I don't know why you have had such bum luck with Ultra Black but this is my only experience with it and I'm now fairly impressed with it's useful life. I'm not certain that Dektol could equal this test, although I haven't tried it. I like UB's tonal qualities, as well. Deep blacks and nice tone in the mid and highlights with Ilford MG fiber.