I had heard that Preston starts getting really obnoxious about assigning settlement quests, and I hadn't gotten very far in the game before I knew that I didn't want to do most of the settlement stuff just yet...I just didn't want to worry about trying to support and protect 20 different settlements all over the map until I'd done some other quests and had more time to explore, collect resources, etc. I wanted to have a nice large bank of supplies and junk first, then worry about setting up a sweet settlement network.

So here's my solution, which is allowing me to pace my settlement development a bit, and also avoid Preston for a while. Note: this only works if you are ok with temporarily postponing advancement of the Minutemen quest line.

-I took Preston around with me as a companion for a little while, doing a few minuteman quests but mostly doing other quests. Eventually I ended up with only a few active, established settlements (aside from Sanctuary and Red Rocket, I had the Drive-In, Tenpines Bluff, and Finch Farm).

-After the third settlement, it triggered the Taking Independence quest, and all Preston would talk about was taking the Castle back. So I told him, sure buddy, I'll help you out. Then he left me to go assemble the minutemen and said he would meet me at the Castle...

-And then I just got a different companion and started doing other side quests and other factions' missions, completely avoiding the Castle location until I decide I am ready for it. This got Preston out of my way, and there are no new Minutemen quests/settlements being triggered while he waits for me to finish this one.

At this point it doesn't seem to have caused any harm to the Taking Independence quest to have stopped in the middle of it, it does not appear to be timed (probably because it is a main faction quest...so Preston will just have to wait for me until I decide I am bored of other stuff and want to do his quests). I can't guarantee anything though...for all I know once I do show up all of the other minutemen will be dead and Preston will be pissed that I took so long. I kind of doubt it though.

So far I have also never had any of the potentially annoying "defend settlement" quests pop up either. I am not sure whether this is just a coincidence, or if it is because I haven't advanced the Minutemen stuff very far or because I am avoiding Preston, or if it is because I have so few active settlements that I have been able to fortify the ones that I have really well and haven't needed to have a ton of food and water to support them. Most of my settlements (aside from Sanctuary) either have no settlers, or have a maximum of two settlers- one to farm and one to run a supply line.

So anyway, this is what is working well for me so far. For those of you who are super annoyed by Preston, try this either now or in your next playthrough if you have already taken the Castle.

Oh and I should also mention that I do fast-travel back to settlements to dump my junk, so if you are one of those people who doesn't fast-travel and wants a better network of settlements so there is always something within walking distance, then this strategy also may not be ideal for you. I do have a couple other settlement quests hanging out that could establish new settlements if I choose (Greentop Nursery, and one other one I forget where), although I don't know if I could finish them without interacting with Preston. I suppose I could have finished them before I accepted the Taking Independence quest, but that would have defeated my goal of keeping low numbers of settlements that I have to support.