...
I've lost a fair number of mostly stable fortresses because I'd go away from the game for a bit, come back, and decide I'd rather start a fresh one than pick up something I haven't touched for months, especially since I get the most joy out of the early game anyway. I'm currently running a duchy, but sometimes that seems more like work than play, especially when so much of the fortress's activity at that stage is passive (except when goblins show up, and I'm very eager for the next siege.)
So, it's complicated.
A final note, and perhaps a word of advice. When my forts get really successful, I think part of it is that I grow them rather slowly.
Likewise for wandering away from the game, then rather starting a new fort than try to relearn where everything is and what I was doing etc. with the old one. Also +1 for the advice, helps avoid migrants of doom, maybe (anecdotal evidence, on the other hand my migrant waves in the most recent fort have been 9, 9, 33, 15, 15, so maybe not that accurate), and definitely should help with sieges etc. I've only had a goblin thief and master thief so far (that I've noticed).
Back on track, my own experience was that I got the hang of a lot of basics pretty much right away, but I did play Nethack quite a bit on and off, so that might've helped. And copious reading of the wiki and the forums too. Now for a long time my problem in developing mature forts is that I'm probably overly OCD regarding layout: I want my layouts to be "neat", efficient yet preferably not boring... I don't like to dig out any "extra" tiles or exploratory staircases or stuff like that. At least not by accident, by which I mean is that if I intend to dig exploratory staircases to find ore or caverns or magma, that's acceptable, but if what I planned to be my main staircase down hits an aquifer, that's really annoying. I also have gotten bored of fort layouts or started a megaproject that was maybe a bit too mega for my patience to get started up, the last one being: channeling down a 81*51, 15-z area around a volcano. I planned on casting an obsidian cube of that size there and hollowing out my fortress inside it, but should've started with a smaller subportion. I have spent a lot of effort building magma pump stacks or rerouting rivers to also have an underground fork underneath my fort, only to get bored with the rest of my fort. This isn't even about tantrum spirals, I've survived a few of those too.
My current fort is really a character test for me, as I try to get over this tendency to just drop forts due to boredom and/or layout OCD. I want to get stable industries (the cloth level is already up and running pretty well, as are stone, wood, and bone/shell trinkets) running, including replacing fuel with magma. And adamantium gear. And surface fort (only 21x31 around this time) done, and secure entrances to all 3 caverns. Sieges I've beaten before, but never really had a well-working goblinite processing system. Once I've done all that, I guess I'll either keep playing, messing around with making some kind of death traps, or since the new version will be coming out at some point (hopefully this year) anyway, breach HFS and see what happens.
I have a couple of new fort ideas, which are possibly quite extensive in terms of layout and one of them a bit micromanagey, but both should be quite modular, so can be built in parts. We'll see if I make those in this version or (probably at least one of them) in the next. I also just somehow lost my mental barrier against major mods today (done some raw mods and bugfixey edits, and recently started using dfhack as well as Dwarf Therapist, for the interface improvements, but no larger mods), and masterwork seems like it would be lots of fun (potentially including !!FUN!!).