I'm surprised someone hasn't already said it for me:
Gregtech
People are gonna bash me for saying it but it prolongs games.
Also, I keep saying that I plan to add a mod to IC2
If I do which I intend fully on doing it, it will end extremely high endgame things
But as to the OP, I would say start a new map and go slower this time.
If you went for example with Pulverizer, Induction Smelter, etc. next time go the Ic2 route or even factorization mod.
Or make a goal like build something huge and awesome. If you're not already join a server.
Lastly, if you do what I plan on doing to cure the "end-game syndrome" then make a mod that will cure whatever symptoms you're having
Hope this helps