I agree. I have run a couple of long campaigns and they are fun, but scheduling and RL attrition takes a bite. It'd probably be easier to do a bunch of semi-connected drop in/drop out modules that each take 4-6 sessions.
And play by post or over Discord, which are both slower? Imagine running Strahd that way. It'd take 5 years!
I have written and tested/gotten through several 6-10 page modules in only 1-2 months via PBP.
It is a harder concept mentally to go "Ok, we're doing this Episodic like Star Trek. Your adventurers are somewhere, and now they're somewhere else, and we don't care that they've moved a hundred miles!"