If you really need a deadline for, say, expansion or migration-- theres always the DISASTER button whereby Sol gets crappier and crappier every year.
Do you play with invaders? They'll keep ya on your toes.
I'm still on my first real game. I couldn't encounter low-tech aliens because I was surrounded by precursors, so I have no idea how my fleet really shapes up or stands up against actual alien races. But i'm getting out there.