It used to appeal to me but I've since revised my view. For me, I feel it would be unhealthy. What you mention about feeling awful a week later.
These events are seriously long. They're unusual in terms of the demands they place and the strain on your body is immense. It might be OK if you're highly seasoned and have run for many years and run a lot of marathons.
For me, in terms of balancing lifestyle, I just don't think it would work.
Like you say, needing a crew, all of the preparation and support. The races also look incredibly expensive.
A lot of the training I enjoyed most was strides, reps on the track, 150m reps, things like that, so it probably wouldn't have fit in anyway.
I spent a while thinking I wanted to do an ultra but I don't any more. I also have had some health issues in the past and don't want to put a huge amount of strain on me again, it just wouldn't be a good idea or sensible.
These events are extreme and should be respected. In terms of the balance I want now, it just wouldn't work at all.
Having said that, I think these races are fine if you know what you're doing, you're healthy and prepare well. There's nothing intrinsically wrong with it. I do wonder why the races people are into tend to be so long though - marathon and so on. I'd have thought something like 5K should really be way more popular.
For me what I'd love to do now is some kind of hike or walk like the Camino de Santiago. I just think it would suit me and my aims a lot more.