tifdickson details the three time periods well. Bill Taylor passed away in Sept of 2009, and it was rumoured that he was in ill health for close to a year. I suspect that Jimmy Craig made most of the 2008 and 2009 pipes, as quality dropped off considerably in the latter years.
My favorites are the 95-99 era. Even so, my first Ashton, a 1998 had horrible drilling, that I was able to fix with some file work. It's said that you didn't want to buy a Taylor era Ashton that Bill made after lunch, as he was apparently known to have a few. (that has never been validated!)
I tried a few Jimmy Craig "Ashtons" (I'm with TF, the name should not have been used past Bill Taylors era) and found the stemwork lacking. Jimmy was at several of the Richmond shows and he had a table full of pipes to examine. Besides him not being very engaged, I also found issues on many of those pipes (2013-2015 era, from memory).
Taylor X sizing was very consistent. Jimmy Craig definitely NOT, by my experience. Jimmy also did a terrible job of marketing pipes - largely selling thru his account on Ebay (he apparently stopped selling on Ebay). For a while, he let several well-known pipe ebay sellers sell new pipes. A German vendor always has a large number of unsmoked Ashton's, so I assume this is now his outlet. Thru these means, Jimmy definitely did everything he could to sully the Ashton name and not exploit the heritage given to him. It has also been rumoured that he let his boys finish pipes in the latter years, again, that is rumour. The pipes I see on Ebay now, do look more refined, but I've not seen one in the flesh to comment.