I'm not sure about that. I do know that being "good" at masking is not the same thing as no longer having masking drain you. Meaning, a person could be "good" at masking but still have it be a mental, psychological, emotional and even physical drain. As such, if masking is still a drain on a person (it certainly is for me and every other autistic person I've talked with), then getting better at it doesn't mean the underlying negative effects of it are gone.
I also know from personal experience that the effects of masking were/are cumulative for me. What was easier when I was younger got more difficult when I became older; to the point that I not only didn't want to do it (ie masking) any longer but I realized that years of doing so was damaging to me, namely to my view of myself, my self-worth, confusion related to my personality or lack thereof (ie pretending to be something that I wasn't).
Here's what I mean:
If an autistic person becomes "good" or "great" at masking to the point that the person can attend a very active, loud, high energy function for hours that involves a lot of communication with others in an environment that is overloaded with sensory stimuli (e.g. a gala, party, "mixer", etc)...and the person masks so well others don't suspect the person isn't NT...but the person is drained afterward rather than loving every minute of it and ready for more, it's not something I would strive for at all, personally. The underlying result wouldn't change for me (ie being drained from such interactions) even if I became the best at masking that there ever was, so for me it wouldn't be an accomplishment I'd care about. I think in a way it would actually be worse for me because of how I'd feel about it.