I used to live several miles from Harvard Square, which was (a) a destination in and of itself and (b) the last stop on the Red Line (back in the day). I used to live about 5 minutes from the Belmont Center route, which ran occasionally, and about 15 minutes from the Waverly Square route, which ran more frequently. However, if I went to the Belmont Center route and walked another 20 minutes, I could get to an intersection served by the Arlington buses as well as the Belmont Center bus. However, doing so involved abandoning the Belmont Center route for about 5 minutes, during which, of course, the bus for which I had been waiting might very well drive by...
Aside from trying to figure out if you got more, less, or identically wet by running or walking through the rain, the question of how best to get to Harvard Square was a central preoccupation of my teenage years. Mathematicians have concluded that I should have waited for the bus.