Then indulge an poor sap who'd like to know more and explain just a little of that. Where, first, does the 8500 year figure come from?
Well, from you, it was your math. Although I have to admit my mistake when I misread "hours" for "years" so apologies. 8503.4 hours, you said.
Secondly, since there is no preferred frame of reference, please explain how the people in your rocket ship can be said to have an instantaneous velocity of zero while continuing to accelerate at 1G. I really would like to know this, so gnomic pronouncements or sneering from others just won't cut it: I'll take your own words or you can supply links or reading material.
Let's do this by way of analogy first. Imagine you are in a boat (I'd have gone with a car, but shifting gears makes for a separate issue so a boat it is), moving in reverse, and fairly quickly at that. The driver decides to suddenly change direction and try to move forward instead. You feel the boat decelerating, let's just say that's at a constant 1G for fun. It continues to decelerate with respect to the land underneath the boat, and for an instant, it's at rest with respect to the land underneath the boat, and then it begins accelerating forward with respect to the land underneath the boat. At all times, it was applying a steady 1G acceleration as felt by the passenger on the boat, but that boat's velocity changed from negative to zero to positive with respect to the ground below the boat. For a moment, it was accelerating at 1G, and its instantaneous velocity was 0 with respect to the sand and rocks underneath it.
You can define a FoR just like that. In fact, if we're talking about a FE undergoing UA, you absolutely have to define a FoR like that if you want to have a meaningful idea of what an observer (like, for example, all people) on that FE would experience. To even begin discussing the velocity of the FE disc, you have to pick a separate FoR and then try and work out how fast the disc would be moving relative to that frame, but that doesn't really make much sense to do, because you can pick any frame you want and say the disc is moving at any velocity you like up to c and all you've accomplished is doing math. It makes absolutely no impact for anyone on said disc. You can do it with a globe, too. There are objects in space moving insanely rapidly away from the Earth. An observer in one of those frames would see the Earth moving insanely rapidly away from it, and it would infer that it has gained a certain amount of relativistic mass, and it has red shifted by however much, and rulers on Earth have undergone a length contraction such that they look much much shorter, but that doesn't affect me or you or anyone at all because we're here on the surface of the Earth, our colors are perfectly normal and our rulers are the right length.