Do you mind me asking how old you are FFN? How did you feel 'coming out' after five hours of VR?
Not at all, I'm 35.
During the first hour I took a short break towards the end. Partially because it was hot, but also because I did one of the BBC Click VR videos which had some weird movement in towards the end and I got an ever so slight motion sickness feeling. My mate (who owned it) said it was better to take a quick break rather than trying to power through. After that I played pretty much straight through with no issues. I came out to change games as I preferred the normal 2D environment for navigating menus, etc... and also to chat to my mate about what to play next (conversing with someone while wearing it is weird!!!). Also you have to make sure the cables we in a good place to start the next game as they can get tangled up a bit (on that note wireless will be a godsend!), but all in I was probably out for max 2-3 mins a time and the rest was spent plugged in and gaming.
All in all I thought it was an excellent experience and I was tempted to buy one afterwards. Some of the things you can do are mind-blowing (genuinely the biggest rush of 'wow' I've had in gaming for a long long time), but equally some stuff was just 'okay' and I didn't feel it gave me more than a conventional game would. The big issue for me is the lack of proper titles available, the short 'experiences' that have been released are sometimes brilliant, but I'm not sure I'd play them enough to justify the hardware once the initial 'ooooh' had worn off, however I think something like Elite would potentially give me that. Until then I won't be investing.
One thing I'd say finally is that I understand the VR experience can be quite a personal thing. I had very little problems but another of my friends literally can't go 10 minutes in the headset before feeling a bit nauseous, so maybe try and get some time hands-on with one to see how you fair.
Sorry, rambled on a bit there. :S Hope some of it is useful.