See, i think the biggest problem here is that most of you have these specific 'goals' you're trying to achieve.
I have never really played modded MC in single player, it's usually with a friend or two on a private server. When we go to play a world, we don't really have any goals. At best, we have some vague notion like 'lets do this thing' or why don't we build something like that sometime?', but never really a solidified goal. Really, we just screw around and do whatever happens to be striking our fancy at the time, which is what Minecraft is best for imo. Because of this, our worlds have lasted for months, even with us on playing for 6+ hours a day at times.
This same attitude usually goes with our vanilla multiplayer or even any of my singleplayer worlds.
Try it out sometime. Start a new world, or join a server, and just do, without any real goals set beforehand.