That's possible.
In the case of one group I'm getting increasingly frustrated and bored. I've also tried other systems to shake it up, but it hasn't solved the underlying problem.
So for that group, I'm planning on one or two more sessions to end it with a suitable climax to the campaign. And then I'm on holiday. (I've been running for them weekly for 3 years.)
The other group is my in-person group with the neighborhood teens and families. I've been running for them for only about 5 months, and it's been delightful (the dragon folding boat incident, notwithstanding - even if that managed to be memorable).
And honestly, it's the neighborhood group I'm most worried about disappointing. We're fostering a teenager who desperately needs this positive interaction with his peers. My wife is having a blast.
I was planning adventures to get us to 15th level and had a second 5e campaign ready to go after that.
That group finds so much joy in the experience, and they're not jaded. They'd probably have a great time even playing an adventure I've rated 1-star.
But I hate seeing the WotC stuff. They're loving the game so much they're buying merch and wearing it to the game, telling their friends how great "D&D" is - and I find myself wishing I could redirect that enthusiasm to another game.
My suggestion is to view D&D like the 22 episode box TV dramas of old. Yes they are rewarding but they can be a slog. Sometimes you just want to get to the point, particularly when the quality of individual episodes is ropy. A 15 level epic campaign can be like that.
There is something powerful and punchy about a 3 season, 10 episode series with a beginning middle and an end. Time enough to set it up, but without trying to be a forever campaign. Choose your level range 1-5 or 6 to 12 or 11 to 16 and do that range really well. Take on your time and enjoy it.
I hope you don’t mind me saying I think you’re a hit of a dreamer like me. I have great ideas, but somewhere between a 1/3 and 2/3 the scale of the task starts to wear me down and I get interested in another project. At that point I’m usually a slogging it out to the end and hating it, or I just call it a day (and feel bad for it). I think more manageable goals is probably the sensible remedy.
My next plan is to run Dragon Heist and buff it out with four or five heists from Golden Vault. Run it more like a Sandbox set in Waterdeep with the chance to descend into Undermountain if they like a bit (chasing specific quests rather than trying to map the whole thing.) levels 1-9 keep it snappy.
My other project is adapting the City of Ubersreik and the short adventures there into a system agnostic place I could use for either D&D or WFRP. I love the bite sized but linked adventures that can re-use some NPCs and make the place more lived in.
Other options to consider…
Adapt the Daggerdale Trilogy from 2e FR. Doom of Dagger Dale and the Randal Morn trilogy - run it levels 1-7.
Run City of the Spider-queen buffed out with more roleplay and more weird underdark communities.
Run Night Below’a first chapter (the evils of Haranshire) but finish it off with a single aboleth/Mindflayer dungeon beneath rather than a huge trek through the underdark.
Convert Shadows over Bogenhafen or Death on the Reik or Power Behind the throne to stand alone adventures. All three would make a good three or four session encounter adventure - longer if bulked out a bit.
