Ron in practise it should only take as long as you are orginized in your Event Browser with all your clips showing and you know what shoots to lay in your timeline. About 1 too 2 hours max.
Very very belatedly and with apologies and thanks to all and sundry here . . .
I'm sure somebody will say I've got it wrong but - I've stuck to Share in FCPX and publishing through Toast because I couldn't find Compressor making any difference to the overall quality!
Hope you all had a happy Xmas and have enjoyed this year so far . . . !