I'm not ER'd yet, but I suspect my ER expenses will be similar to my expenses now...well now that I've cut them down since getting serious about FIRE. Some costs will go down (commuting), some will go up (I'll have to start paying for cell phone service, a gym(?) which is currently available at work, on my own for health care), and some will stay the same (such as food as I think I've got this down pat).
My travel budget may expand a little since I will have more time to travel. My charitable donations will go down since I do it as a percentage based on my income.
But I don't mind an initial increase in expenses in EARLY retirement (such as for travel), as I believe in maximizing my time in my 50s and 60s. I plan to taper my costs down a lot in my 70s as the type of travel and activities I can do might be curtailed by a smaller stash (from spending it in my 50s and 60s) and possibly deteriorated health. We have long lives (into the late 80s and 90s) in my family, but I don't mind spending those last 10-20 years enjoying my local surroundings, moving in with friends/family ala Golden Girls style, etc., in order to reduce costs. If I do happen to have the money and health to travel in my 70s that would just be an added bonus.
This coincides nicely with Social Security. Maybe I can just live on that in my 70s and 80s if the stash unexpectedly does not last that long. From what I see in my family, those two decades are best spent slowing down and enjoying life.
I'm also not a big fan of going to extreme measures to extend my life. Some may call it morbid, but I will accept whatever comes my way once I hit 75 or so. So I won't need a huge amount of money for end of life care or anything like that. Although like I said my family history seems to indicate I will be healthy into my late 80s.