How many years have you had him on your team?
Loyalty means nothing until after 5 years, so you're asking the wrong question.
You need to know whether anyone has ever lost a FA to whom they offered the max deal after that player had been with them for (at least) the entire prior 5 seasons.
If you ask that question, I suspect you won't have anyone answer "yes" - check that, I suspect you won't have anyone answer "yes" and be able to back it up (people will always say "yes").
If you haven't had him for 5+ seasons, budget accordingly. Is 90 the best hitting coach available? If not, cut him loose and go get the very best guy.
With pitchers it is pitching coach and bullpen coach that win; hitters it is hitting coach and... fielding and 1B/3B? Just fielding? Just 1B/3B? I'm not sure. I haven't had to worry about signing a hitter to a max deal before.