I've been dreaming about a really long bike for awhile now.
I have five children, ages two through ten. The oldest three will ride with me--the longest trip we've made together is 4 miles each way (with a picnic in the middle). I don't think my wife has ever gone further than that, either, nor is she all that comfortable with traffic. But that's when we have lots of time.
While we don't drive a whole lot as it is, I'd like to drive less and ride more, and I'm wondering whether it would be worth our while to buy a Bilenky triplet/quad that's available. We currently have a tandem, which is great for taking my daughter to ballet school, avoiding conflicts about who has to ride behind whom. On those rare occasions when my wife and I ride it without any children along, we can really get going. It's a lot of money, but my wife seems willing (if I let her buy plants for our garden). Specifically, if any of you have bicycles of that magnitude, I'd like to know whether it makes a difference in how often you ride (as opposed to driving), and whether it's substantially faster than riding with children on their own bikes (given that they won't be supplying all that much power compared to the weight of the bike.