Most NOS tubes are burned in by 30 hours. Some quicker, some longer. But, most are stable by 30 hours. Yes, let the tubes warm up for stability and better sound. There's not much risk in turning them on and off in a short period, but I don't do it just because I'm pretty anal about things.
As far as rolling options, after you start with the stock GE, your next attempt should be the Sylvania 6DJ8. Those are great tubes that sound nearly as good as the ultra expensive and rare birds.
To all you glass tube addicts out there:
Well, I will begin with Jason's succinct recommendation first, the NOS GE's that come as one of the options, to establish a "baseline" sound signature through my equipment/ears/brain, and then attempt to compare that with what I read/gleen from the tube rolling thread, and hopefully draw some reasonable conclusions regarding what I might like to hear next...though without even hearing a single tube yet, those orange Amperex tubes seem to be singing like Rhinemaidens...
Being a newbie tubie:
(1) When should I expect these NOS tubes to be broken in?
(2) During normal usage, do these tubes need some warm-up time prior to listening, either for the ultimate health of the tube, or for the sound qualities to be maximized?
P.S. I contacted Schiit Audio around 2:00 P.M. on Monday, received Jason's tube recommendation within an hour, ordered within the next hour, and by 8 or 9 P last evening received an e-mail indicating they had shipped!...maybe my requesting tube advice and selecting 2nd day delivery convinced them that I was hooked...lol...(I AM impressed with their promptness!)