Is this one of those games that allows you to keep playing after you've finished the main story?
Ive been doing a lot of the side missions as they come up, but I'm kind of ready to just focus on the story and finish it off. But I don't want to miss out on all that side material, I just want to wait and come back to it. 
Yes. After you beat the main story and sit through 20 minutes of credits, an epilogue will come up and after that you are free to roam with Conner again.
Good luck getting through this game. Beautiful and all that, but the exact same as previous AC's. I gave up about 10 hours into the game.
Same here. Beat the main story in about 13-14 hours. Thought it was excellent. Looking forward to the Tyranny of King Washington DLC. 