I think they generally hit a peak. Is SVB better now then a few years ago when he ran the 7 pack and 2 6 packs on Alex in the TAR match on the Fatboy rails in 10-ball? I don't think so.
They of course can learn a new thing or two. They might tweak a break, learn a new way to make a kick with a certain bit of English, but they reach a point pretty quickly where 99.9% of their total ability is already there.
They still deal with the highs and lows. They have moments where they are on, and moments when their game is not at the peak. TBH right at this moment I do not think SVB is at his top level given his last few outings. He has not been as dominant as he was in the past and I am not sure the loss of the race to 100 action matches has helped him, those were an awesome way to stay in stroke and keep your confidence up.
One thing to consider is his strongest game is 10 ball (because of his break) and in my opinion he's the best 10 ball player in the world. I don't know if 10 ball will stay popular but the loss of some of these 10 ball tourneys could also be a factor in his results.