In days of yore when one was posted to an Aerodrome there wasn’t much likelihood of being forcibly relocated to another unit - it would generally be about when/if you wanted to move on.
With the advent of digital/remote towers the prospect of “being moved on” becomes increasingly significant until the point is reached of Remote Tower Centres. HIAL are effectively pioneering this trend in the UK - I’d, personally, be surprised if NATS don’t also go down this route. Some airports will no doubt choose to keep their ATC staff nearby, others will see the benefit of relocating to an RTC. Swings/Roundabouts.