My advice is not bank on OT. Its wonderful to make big bucks but if you out spend your income you are always trying to make ends meet. Make a plan, have a budget, if you make more than you budget for, then save some for tighter times and stick with your plan. If you spend pay check to paycheck then you will run into problems sooner or later. always plan a little towards retirement. You have to raise the kids, send them to school, feed the family, keep the transportation running dependable, repair the roof, have some fun and save some. if you base that all on OT , when OT dries up you are boned.
I guess it hasn't much to do with being in a Union or not.