I grew up with a fairly strong regional accent. I went to university in my own region but it faded there, mainly because I was mixing with students from another region. Eventually in my twenties I ended up working in London with an accent that was all over the place ( short and long As galore) before returning to my home region with RP with a hint of my original accent.
Hope that makes sense. (I try not to give locational details to keep anonymity).
None of this was ever conscious. Just wondered how others' speech has evolved.