I have 8 hills on my round trip to my office (4 to and 4 from). I usually have enough energy for the first 2 in both directions, and the last 2 of each leg becomes a bit of a slug. I still rather use my legs wherever possible, but coming to terms with age, damaged heart (3 stents), wear and tear on my body, and prefer not to reek of sweat by the time I arrive.