To each his own, I suppose. I've been deskless for 4 years, mostly on a couch in a relaxed position with laptop on my, hmm, laps. It's much more comfortable for me than chairs and desks. I sometimes spend 16 hours per day pressing those keys; I don't think I could've survived that in a chair behind a desk.
You still need to be careful: 4 years is not that long. Middle Ages people were exposed to very harsh environments and still lived to 30.
I started getting neck pains after 11 years into my programming career. I attribute it mostly to programming on a sofa with a laptop -- in this position you constantly look a bit down (if a laptop is on your lap) and your neck will not like it.
