It just seems as convenient and potentially less wasteful than using a whole 36 frame film of identical pics as a fallback test each time but OK everyone to his own test
Don_ih did not suggest "using a whole 36 frame film of identical pics as a fallback test
each time".
What I do (and my understanding of what Don_ih recommends) is to plan forward and shoot one roll of identical as-metered exposures of a blank wall on an arbitrary film (FP4 in my case). Also develop one frame in known good developer; net density should be something like 0.65, but that is off-topic.
If and when in the future I have doubts about a developer (old, new-to-me, whatever) or a roll is especially important, I take out the cartridge from its black plastic (or metal) canister, in the dark (so as not to waste the ~8mm long piece sticking out, pull and cut a ~40mm length, return the cartridge to dark storage, and the film snippet goes into another black plastic canister, to be used as a dev tank (25cc). Half an hour (or less) later,
- visual comparison with the reference snippet is good enough for a go-nogo test
- if so inclined, measure B+F, density, net density, and compare with reference.
In summary: one 36-roll buys me 36 future tests.