if for you 8hours is fulltime, you might be thinking of priesthood as a job.
well.. it's not. its a vocation.
got this from butitoy...
There is an ocean of difference between having a day to day normal job and from having a vocation. Vocation is a calling from God, a personal challenge for you(the priests) to shepherd His flock, which in all case the Catholic church deem necessary and by common sense and universal law, our church deserves the soul right for determining this because we as an institute manage our own from internal magisterium, and does not need any opinion nor influence from outer source of ideas, to put it on compulsory requirement, as stated by the church canons pertaining to celebacy to have our priests maintain a single-blessedness state in life.
Bottom line, this inquiry has already been sufficiently answered by our church, even with the absence of necessity that it may hinder our existence but out of answering dire ingenious curiosity and criticisms.