Hi Paul,
Absolutely! I must be on about the tenth iteration of my new embouchure. Each time I go back to Largo my first reaction is “I’ve failed – again!” but really it’s just a refinement of what went before, and it always takes a couple of days for that to sink in.
I’m always hoping that this iteration will be “the one” – that big breakthrough that opens up all those notes I used to be able to play with my old (tension/pressure) embouchure, but as you point out, progress is never linear. There are definitely improvements in my new technique and the exertion and sound quality are much better than they used to be. I just don’t have the range – YET!