In the comics, Guard will retire. Some will seek simple lives, others will move on to politics, families, etc.
The other Guard will have feelings about the departing mice in any emotional direction. Some may feel abandoned, others will feel grateful for the time they had together, some will think “good ridance” it all depends on 1)the mouse leaving, 2)the mice who are judging, and 3)the circumstances/setting for the departure.
You are welcome. I would also say that Guardmice tend to stay Guardmice for quite some time. It should be rare that one would cease to serve if they had felt the call so strongly to join.
Retirement should have more to do with major events.
-Having completed a remarkable number of years servce
-Having survived a war or massacre
-being called to another duty
-having a falling out with current guardmice
I would say that unless the mouse leaves under bad terms, the Guard will always hold that mouse as a Guard at heart.