10,000 hours divided by a 40-hour work week = 250 work weeks.
250 work weeks divided by 52 weeks in a calendar year = 4.8 years.
I get it that the "40-hour work week" is an antiquated idea, but Ingmar, I would speculate that Wally's time with his coffee mug - based on these rough calculations - is well into overtime and deserves comp time.