Once linked to a workstation, villagers will not unlink from workstations even if workstation is removed or villager is moved 1000 blocks away.  Villagers still link and unlink from beds.

Edit: 

Maybe it's more accurate to say Villagers don't lose jobs after unlinking from workstations.

Example:

1 - New villager is bred

2 - Baby villager is removed from breeding area (100 blocks)

3 - Villager becomes adult non-nitwit villager

4 - Composter is placed, villager becomes farmer

5 - Composter is removed, villager remains farmer with original trades

6 - Villager is removed from area (1000 blocks) villager remains farmer with original trades.

Also, if I go to a village and remove all workstations, villagers still retain jobs with original trades. All villagers in all examples have never been traded with.