>1) as I begin to add supers, is there a point where there are too many supers on a hive?
You could give them too much excess space. You could get so tall you can't get the supers on and off.
> I guess what I'm asking is - at what point do you remove supers?
I try to not take them off until the end of the season. That way I only have to extract once. Cleanup is time consuming and wastes honey.
>Could the answer be as simple as to remove them once they are full?
>Or should I keep putting supers on until I harvest in the fall?
That's what I do.
> My fear is that the hive will get too tall.
You can hope. I've seen it once or twice in the last 39 years...
>2) I kept 9 medium frames of capped honey from a super from last fall - this was going to be for emergency feeding if I needed it but as it looks now I may not need them. They currently are in the freezer - frozen solid. What should I do with frames?
I would let them thaw in the kitchen, and then put them on the hives.
> Would you put three each in the supers that I add in the spring to each of the three hives? Should I just allow them to thaw then harvest the honey from them now? Please advise.
You can harvest them if you like. The bees tend to burn a lot of stores in the spring raising brood, if they need it, I'd give it to them. If not, then I would harvest it or give it to splits later to get them a good start.