All of IIRC, all of the Nike balls have a durability of 2.5, which is equal to 120 hits.
Putts Putts don't count as hits, unless you use the Mulligan feature in Practice mode.
Your Your scoring average is 67.7, so if we figure 30 of your strokes per 18 holes are putts you use up 37 or 38 hits of ball durability per 18 holes.
120 / 38 = 3.15 - 18 hole rounds per ball, or 56-57 holes of WGT golf as long as you don't hit a ball OB or lose a ball in a hazard.