Sometimes it feels like that for me as well. I may not lose the movement itself or the speed, but I seem to lose accuracy. I wonder if it’s the same for @Bill_hall, whose technique looks so incredibly consistent from one performance to the next! Perhaps this is an advantage of using a primary elbow mechanic, since the elbow joint is as simple as it gets?
Bill, would be great to have your thoughts on this 
Thank you @tommo! For me it’s pretty consistent overall I would say… But I do play a lot, LOL! I would say the difference for me isn’t really accuracy or anything like that but more how fast I can play. On any given day I can play 120 to say 130 consistently for a long time with the metronome as sextuplets say, but some days the 130s or higher are a lot easier than others, LOL! Almost all my practice is usually in the 110 to 130 range on the metronome say if I am playing sextuplets, so maybe if I practice with the metronome set higher it would make a difference, but I really don’t feel any need to do that because I don’t really have any need to play faster than that.
Although if I’m playing live sometimes it’s so effortless because maybe I’m pumped up from the crowd. I do think one advantage to the elbow technique is that the pick speed is always kind of available because the motion itself tends to be very fast if you want it to be. But some days are a lot better than others that’s for sure, LOL! I think it’s more that way with all of us, I know when I work out some days I can lift a lot heavier than other days and I think we’re probably all like that. Also the mental mindset I’m in makes a big difference also. It is an interesting question though. But I always just aim for a consistency at a speed that’s fast enough that I could go faster if I need to and where I’m still using the mechanics that I use when I play fast and that’s generally where I practice and play.
I really want to get the ‘inside footage’ from the interview and check out some analysis of your playing. I find it endlessly enjoyable to listen to, especially since you seem to favor the acoustic (at this point anyway) but you’re clearly a shredding monster 
and I really can’t get over how clean and crisp of a tone you have, even on the really quick runs.
Thank you so much @JB_Winnipeg! I really appreciate that very much! I love playing the Acoustic so much…it sort of has a timeless quality to it that I like and I find it really fun and expressive to play. I work on my tone and Phrasing a lot. The tone on the Acoustic really comes down to how you hit the string when you pick and making sure the left hand fingers are right up against the fret for the most part. I find on the acoustic that picking without using a lot of edge picking really gives an even bright sound. Although it might just work that way for me. Thanks again! 
From this link: https://www.guitarworld.com/artists/dear-guitar-hero-vinnie-moore-answers-your-burning-questions he talks about his right hand technique and how he can still play the old stuff.
I noticed your right-hand technique has evolved throughout the years, and you’re now incorporating more hybrid picking into your playing and doing less straight alternate picking runs. As your technique has evolved, can you still play all the stuff from your first couple of albums? - luis m. “My technique did change. Using hybrid picking is something I’ve always done, and it’s crept more and more into my playing, but it’s not really a conscious thing. I can still play a lot of the early stuff, but I wouldn’t play it that way. I’d just use alternate picking for those songs!”
His legato still the same - and awesome!! check this out:
Thanks for sharing, can’t get enough of this guy!
By the way there’s also a glimpse of his shreddy picking at the end!
Here’s Vinnie doing some alternate picking in a version of lifeforce in 2018.
Seems pretty good to me! This lends credence to what @BillHoudini was saying above people’s tastes changing.
Maybe Vinnie is just not into speed picking as much these days? Seems he can still do it.
Be interested in @Bill_hall 's take on the above 2018 performance in reference to his retrospective on the original Minds Eye recordings above…
I think that clip is awesome, @Interestedoz! I I love it! I think it is just a matter of his taste changing because clearly he can still pick fast whenever he wants to! If he really focused on that again he would be playing that stuff exactly like he did in the old days for sure! He’s just into a different thing now which is cool also! I have seen other live clips of some of his recent playing and he’s doing some great fast picking and those video clips also. Great stuff!
Great job, Bill! You’re a fantastic player!