Having chosen to stay with Sam after the end of the battle for the Allspark, Bumblebee made arrangements to stay close to him at all times. It's been a pretty good deal. He gets regular detailing, and as much high-grade fuel he needs. Plus, he gets to spend time with Sam and Mikaela. His vocals processors still aren't fully up to snuff, but he and his friends communicate just fine. If he even misses the action of battle, he can always give Ironhide a call and go Decepticon hunting.