Code:
/run for i=1,40 do local n,_,_,_,_,_,x,_,_=UnitDebuff("player",i);if (n=="Sated")or (n=="Exhausted") then SendChatMessage("OMG WAIT"..format("%.0f",-1*(GetTime()-x)).." SECS ON THAT BUFF!!!", "RAID_WARNING",nil);
that'll throw up the warning, you can't put /cast in there cause blizz protection will lock it out during combat. It will however work to send you a message, just put it on a modifier of the button you use to cast and you should be good to go. Hope it helps. Comes in around 211-215 chars as is so no need to use crazy addons, and you still have a little space to mod the message should you want to.