i've played over an hour many times, the worst that happens is my forehead gets sore from the headset resting on it, even when it's not super tight. there's no going back from this feeling either, needs about probably 20 minutes without the headset on for it to feel relieved, you feel immediately relieved after taking off the headset and it's really not that bad, it's the same as wearing anything tight nearly anywhere on your body for a period of time. that's usually my cue that i've played too long anyway and it's about quittin time.
I don't have any visual issues. I wear contacts as i'm near sighted, it's better to wear your contacts as the viewing then is consistent in both eyes for better viewing experience if your eye strengths differ. I can easily tell a difference in this.
I feel you get more immersed in the experience after about 5-10 minutes.
vr is awesome.
I have the Lenovo explorer.