How many times can rod and main bolts be torqued?

Think of the oil clearance between the rod bearings and journals. You're talking on the order of .0015"-.002". The rod bolts are either pressed out or gently knocked out with a brass hammer. Either procedure can tweak the big end of the rod. Also, minute differences in the rod bolts diameters will place the rod caps in an ever so slightly different place than the old rod bolts. When you're talking about thousandths of an inch clearances, the least little change can be a big one.