Yes, my accent has changed over time, both consciously and unconsciously.
I grew up in a small town in western Pennsylvania, an area with several quirks in pronunciation, vocabulary, and even, I think, grammar (if I'm remembering the academic paper correctly).
When I moved from western Pennsylvania to the Pacific Northwest, I very consciously changed my pronunciation of several words, mostly in response to misunderstandings or strange looks. (In one case, a friend said "Aw, it's cute how you say 'onion'.") The "accent" is usually an issue of vowel positioning. Close, fronted vowels end up pronounced more centrally (or maybe more open? or both?) where I grew up, because that's where I seem to run into trouble.
So, where I grew up, "feel" and "fill" both sound like fill, "steel" and "still" both sound like still, etc. One time, a roommate here in the Pacific Northwest asked what my high school's mascot was, and I said "We were the tigers." The more standard American pronunciation of tiger is /ˈtaɪɡɚ/ but I had learned to say it as /ˈtæɡɚ/. So I said (what I thought was) "tigers" and my roommate heard "taggers." She was pretty confused.
I went back to my hometown last fall and ended up staying longer than planned. My accent reverted back a bit, which was definitely an unconscious change on my part. I didn't even notice it until I returned to the Pacific Northwest, where I've lived almost 20 years, and someone who knew me fairly well commented: "You've got an accent now!"