That's the advantage I've found with the London Underground, unlike pretty much every other public transport I've ever used, there is very little waiting time. I don't think I've ever waited more than a couple of minutes for a tube train. So you can plan journeys using several different lines without having to worry that changing trains is going to cost you half an hour!

Even in Newcastle with the metro, they don't have enough trains so it's often nearly a 15 minute wait sometimes.