2024’s spread is almost identical to 2020’s. just without Florida(which was still considered a swing state then). 2016 was a broad year with something like a dozen states considered gettable, and a couple states that ended up flipping weren’t even supposed to be swing states. 2012 only had a handful, I think even fewer than we have now, like 4 or 5. 2008 was another broad year.
Only way it can change is either if a swing state tilts hard enough to no longer be one(Michigan being too blue) , or a formerly safe state tilts enough to be up for grabs again(something like Virginia or Texas)
There isn’t even really a hard rule for it. Iowa was excluded in 2012 because it was going so strongly for Obama despite being a classical swing state, then it was back in 2016, then it was excluded for being too far right. Meanwhile Virginia had to go blue 3 times in a row to stop being considered a swing state.
Nothings set in stone. Most of the current swing states haven’t even been swing states that long. California was considered a swing state in the 90s. Texas was a swing state in the 70s. Oregon was a swing state in 2000. Iowa and Ohio and Florida were THE swing states until they all went safe red. New Hampshire was on that list until it became safe blue.
Virginia was a safe red state from the late 60s until 2004 when it was a swing state that went red, then it was considered a swing state through the Obama years(despite going blue it was redder than the nation in 2008 and about the same as the nation in 2012, had a Republican won either year it would have gone red) and after Hillary carried it safely in 2016 it’s since been considered a safe blue state. Heck, there’s some evidence it’s re-tightening again and a non-Trump Republican could take a serious shot at it in 2028.
There have also been periods of American history with basically no swing states and the bulk of the country up for grabs with only a couple of ‘safe states’ each if that, the 70s and 80s didn’t really have swing states, neither did the Depression Era, but I don’t think it’s trending that way