There's a Starfield bug that makes it crash more often if you don't start New Game+

Stop me if you've heard this one before. The longer you play this Bethesda RPG, the more unstable it becomes. Am I talking about Oblivion's reference bug, or Skyrim's PS3 lag bug? (That's our brand director Tim Clark there holding Bethesda's feet to the fire on the latter.) Nope, I'm talking about Starfield, where players who have racked up hundreds of hours—not that uncommon in a Bethesda RPG—are experiencing more crashes the longer they play.

This was brought to our attention by a couple of modders, including wSkeever, who added Doctor Who's weeping angels to Skyrim, among many other delightful mods. It was wSkeever who brought this bug up on the Starfield Mods subreddit last month, noting that, "I've been investigating an issue experienced by me and several other people where long running saves without ng+ would experience more and more frequent crashes during play."

The cause is apparently the way Starfield generates dynamic form IDs. These are codes every unique object and location has, and which Starfield uses to keep track of their current state. Drop a medkit and Starfield remembers where you left it because of the dynamic form IDs. The more of them there are, the more bloated and unstable your save file gets. Normally they'd be recycled after a certain amount of time to prevent that—which is why you have to be careful where you store loot in Skyrim. Some containers remember what you put in them, while others will eventually put the form IDs of whatever is in them back into use.

This is a bit of a simplification of course, but it seems like Starfield isn't recycling form IDs the way it's supposed to. As SpareDifficult9987 put it in a post on the main Starfield subreddit, "What will inevitably happen, is that the ID generation will start to run out of numbers it can use for the ID's it needs to designate. This will cause your game to crash, and the more you play, the shorter the intervals will be between crashes, practically making your save file unplayable."

Currently, the only way to deal with this is to start New Game+, which resets every single form ID. Continue playing for long enough and you'll encounter the same problem, however, necessitating another New Game+ restart. 

A community manager at Bethesda responded to complaints by saying there's a stability fix for a memory leak bug coming in a patch next week, and "the devs are investigating a separate issue relating to Dynamic Form IDs that is preventing people from successfully loading their saves and hope to have that fixed in a later update. Additionally, they're actively looking into long load times on Steam, and I've passed along a couple saves from the community for them to check out."