It said "start-ups" which I took as meaning plugging in the machine/turning it on. 511 games in a highly trafficked arcade wouldn't last very long.
Either way it would have been easy for the arcade owners to know there was something fishy going on. If after 511 times all the wack-a-moles bought on the same day would have failed. If it was the amount of games played, they'd all fail within a month of each other.
All the games would be failing a year and a half after they were bought so even the company he worked for would figure it out.
I second SavannahLion idea. He should have waited until the counter hit 500 and then have the games fail at a randomized rate. This way they won’t fail to soon. Some would fail close to 500 days others would fail years later.
Doubling his rate after a year was also a little obvious. Using the randomizing, he could have gone up slowly so it wouldn’t be as obvious. Whoever was luckily enough to have a machine that didn't fail right away, would end up being unlucky by paying higher fees.