If they haven't given you any problems then there is no need to replace them. The nice thing about hyd., roller lifters is that you don't have to change them just because you are changing the cam. Give them a look over while you have them out. Look for signs of wear, check to make sure the rolloers roll smooth and keep them soaked in fresh oil until you are readu to put them back in. Don't let minor scuffs on the sides of the lifter body scare you away, its normal.