Rolex Oyster Perpetual Datejust not keeping time.?

I had my watch cleaned, re-calibrated and new crystal put in last year at a cost of $650 and after a short time started losing time. Most of the time I wear it at least twelve hours a day. The only time it is off my wrist is when I am at the beach for a few hours in the summer. Was told when I purchased it 20 years ago that it must be worn minimum 6 hrs a day to keep time. I was told you should only wind it when it stops. The jeweler that cleaned it said I should wind it 15-20 times, once a month. Any incite as to what is wrong with it and what steps to take to alleviate the problem. Also, what is the correct way to wind it.