I stop doing the quests once their objective reads "Talk to Preston". According to Radio Freedom, 'all's quiet in the Commonwealth' after you've saved those two settlements but haven't told Gravy about it yet.

They do actually have some kind of a limit, though I don't know what it is or how it is determined.

I was grinding Minuteman quests for Strong and Curie because normal exploration generated nothing (Curie) or was even detrimental (Strong doesn't like lockpicking) and I didn't want to break character to please them. Eventually Gravy and Radio Freedom stopped giving me quests, and I travelled with someone else for a while before there were more.

Seems, you're expanding too fast. Confine yourself to Sanctuary and Red Rocket for the first 10 hours or so. Ignore what Preston hands out, since the last thing you want is overstretching yourself. Invest everything you have into Sanctuary being your model colony by upping your perks and by building water purifiers all along the river. You're harvesting clean water in the hundreds in no time and can sell that on for shipments of rare supplies. When you stocked up, expand slowly, one step at a time.

I stopped reporting back to Preston. That stopped the quests for now. But sooner or later I have to go back to the castle, and then I guess he'll be on me with new quests..

Sure would like a mod that makes it so I must ask for the quests from Preston.

Shoot him in the head that should stop them can't give you quest if he's dead

I managed to stop the quests by turning them in and carefully sprinting away just as he starts dialogue for the next ones. If you time it right you can avoid picking up the next quest. After that, don't go to the castle, or listen to the radio lol.

I think this might have been a slight design flaw. They are meant to give the sense of urgency and having hands down approach to the settlement managing and for play tests, I would assume the first two-three times its happened it's just been "awesome, this game feels immersive" .. .. and no game test tests the long time effects. Which is mostly aggravating. Not being able to return a quest without automatically getting a new one is just.. argh..

Don't listen to the Radio Freedom. There's a switch on the radio tower, look around, you'll see it. By shutting it off it shuts the speakers off so you don't hear it.

I'm thinking of doing that. I finally did 2 quests hoping to be done, reported to him and he gave me 3 more.

I'm curious what people though they were signing up for when they agreed to help rebuild a commonwealth spanning mutual defense pact if it wasn't constantly getting roped into defending the commonwealth.