"Oh, they don't count at all," The Doctor teased, grinning a bit wider at the Time Lady. "Book smarts alone can't get you out of half of the situations I've found myself in." Really, when it came to most of those situations it was less that The Doctor somehow ended up in them and more that he got himself into a good bit of trouble nearly every day.
"No one can do this forever," he said simply when the subject turned back to the fact that he traveled alone. "Aside from me, that is. Eventually people have to live their own lives." And, yes. It did seem like many of his old companions he had run into after they parted ways had continued to lead a life of adventure and hunting for aliens, but at least they were with their families. Even Rose, locked away in another dimension, was with her family. "And I'm never alone for that long anyway, you know that." He added a grin to go along with that last bit.
And those blasted trait thieves. "Apparently they conquered Bessan. I wish I could have stopped it."