Yes that is the problem, if you can't get good fresh film from B&W, where then?
However, threads and posts by folks that say they use a lot of TMZ indicate that it almost always has a dense base and are still happy with results. I was looking at some prints from negatives shot in 2003 on TMZ the other day and thought I should use some more of it. If I get some I'll do a side-by-side test with some other 400 film for a comparison like this test. I looked back at my notes and the last time I checked TMZ I plotted it on graph paper as it was before I had a graphing computer (1986!).
I'm not showing any of my tests because they are probably too old to be of any usefulness. I'd be more excited about the film in its manufacturer would give some indication of long term availability.
This is how Kodak reported its performance compared to T-max 400 (first graph = t-max 400. Second graph = TMZ):
Source: Kodak website
(Historical note in case someone finds this thread in ten years. Kodak filed Chapter 11 bankruptcy a few days ago.)