A legal phrase // Legale dictum
[servire] quamdiu bene gesserit = [to serve] for as long as he behaves [will have behaved] correctly
[servire] quamdiu nobis placuerit = [to serve] for as long as he/it will be pleasing to us/me [i.e., "at Our pleasure"]
I'm writing in Latin hoping for correction, and not because I'm confident in how I express myself. Latinè scribo ut ab omnibus corrigar, non quod confidenter me exprimam.