Update:
lvl 88 warrior. Put him in shared exp in the fellowship then logged him off.
Have three toons who are max AA and Lvl, put them on share too.
Later, when I looked at the fellowship, I noticed he was listed as "Capped"
So last night just after midnight I brought him over into the group and let them rip.
Around 5am they stopped for some reason. I got them going again around 9am and by 11:30am he had used up all his fellowship credit, no more green line.
However.. he is now lvl 95!
With no exp potions, no LoTD, just fellowship credit that would have been wasted anyway. He leveled 7 levels in about 8 hours.
The exp messages that I get when running Kiss usually show "<< EXP: 0.30% AAEXP: 0.00%" every other mob.
With the fellowship credit I'm getting "<< EXP: 1.24% AAEXP: 0.00%" to "<< EXP: 1.41% AAEXP: 0.00%" per mob!!!! Roughly 4 times the exp.
If your main toons are full AA and EXP, you're wasting exp if you're not in fellowship and sharing!