I abandoned Gorgethorn a long while back because of the framerate, and I haven't bothered playing DF since because I realized if I didn't change my ways, all my fortresses would suffer the same fate as Gorgethorn, and I would never get to make anything cool before the framerate made the fort unplayable. Instead, I've thought deeply about a number of things.
I have realized that the greatest flaw in my playstyle is that the Great Obsidian Block takes forever to create: one of the reasons it takes forever is because I tell myself that I need to mine out every layer between the first all-stone layer and the first cavern so that they may be filled with obsidian. But when I think about, all I need is 3 layers of obsidian: 1 for the nobles, 1 for the commoners to sleep in and 1 for the commoners to eat in. Heck, I might even fit the dining room in the same floor as the nobles and only need 2 levels of pure obsidian. I waste my time not only strip-mining, but in setting up "temporary" accommodations for everyone that end up being permanent. The other reason that I have to build a magma pumpstack hundreds of Z-levels high. There's also the issue that my habit of mining out everything makes pathing cut down my FPS.
I resolved to start playing again once exams are done, and when I do, I will make my first volcano embark. Even if I have to rely on the first cavern layer for water, I will save time on pumpstacks. I will cast only 2 layers of pure obsidian (well, 3, so I can have obsidian floors) and set up rooms for everyone as quickly as possible. In fact, I will try to set up every industry and storage space as quickly as I can, and I will learn to use traffic designations for the sake of my framerate. Additionally, I will leave INVADERS toggled to YES, forcing me to set up caravan-friendly defenses quickly. If I do all that, perhaps then I can finally build a proper fort, and not just works-in-progresses that I never finish.
I also thought about what brought my framerate so low in Gorgethorn. Using graphics for the first time and playing in a larger world than usual probably did it, so I guess I'll go back to ASCII and smaller worlds. The number of tame animals must have reduced FPS in all my fortresses, though; perhaps the caverns do not need so many extra species after all. I will keep my belzugs for their valuable shells and milk, but I'll get rid of my other custom species, as well as the cavern species I always hated. I also hate fliers, so I'll get rid of every last one of them except for rocs, and I'll give dragons and cave dragons flight just to keep things interesting.