I've heard of it. I haven't really been into distance for most of my short biking career - that might be changing now as I have been going further, but nothing like you are referring to. My longest ride was 103 miles (9 hrs 11 minutes of riding but well over 11 hours total).
Being on Hawaii, going to the events you mentioned would be far too expensive, even if I got into riding those kind of distances.
I would guess that riding in a group would be more fun as well as faster, but my rides start between 2:30-3:30 in the morning! It's the only way to avoid major traffic problems here. A few times I've ridden with one or two others - usually someone I came across on the ride - but usually if I meet someone they are either going much faster than me or I'm going much faster than them.