If your FI was a 71 and wanted to stay would you keep him or let him go in hopes of getting a better one?

Depends on patience and discipline rating; depends on whether I want to win now and save a few million, or if I have minors rich in position players and don't have anything else critical to do with the money.

That said, I'll almost always keep someone like that.

Not I. Development of my players is so important, your fielding instructor is for all levels of prospects including your big leaguers. Its a big hit but its an important one. Pony up the 3-5 million and get someone that is a minimum 85 fielding. Worst case, there are some Bench Coaches that have over 80 fielding that you can probably get for under 3 million. The won't re-sign but its a temporary solution.

Depends on the situation.

I'm keeping a 66 because my payroll is 99.9m and I have 22m in potential arbs. I also have 8m in FA I might want to sign. Saving 3m on a FI will make a difference.

Also keep an eye on available coaches and job openings. Sometimes you get down to the last cycle of coach re-signing and realize your incumbent doesn't look that bad, and would actually be one of the better free agents.

Every season seems like a handful of coaches get stuck with an FI with an under-60 rating. You don't want to be one of those. 70ish might not be ideal but I don't suspect it would actually harm your system.