As I keep telling my 7-year-old, a joke repeated too many times loses its zip. Nonetheless, I have to dip into the realm of cheapskatisms once again to head off a brewing scandal.

My Cheapskate of the Year and I are a couple of frauds, according to a parade of readers who think we cooked the books.

“Your cheapskate champ is a chump: he didn’t calculate the complete costs of reusing dental floss (yuchhh!),” one reader wrote.

“I don’t think you make a good investigative reporter,” another sniped.

In case you missed last week’s column, I awarded the grand prize to Peter Nowak, a retired Willow Grove, Pa., metallurgist, for his method of conserving dental floss.

He starts by tying it into a loop to avoid the waste of the standard method of wrapping the ends around the forefingers. He finishes by sterilizing the floss in a few drops of rubbing alcohol so it can be reused.

Our critics contend that the cost of the alcohol could outweigh the savings in floss.

“According to Mr. Nowak, he saved $5.06 per year using this method,” one reader said. “A 16-ounce bottle of rubbing alcohol will run about $1. If he used just one-quarter of an ounce each day to clean the floss, he will need a new bottle of alcohol every 64 days.

“Based on my calculations, this means he must use about 5.7 bottles of alcohol per year to clean the floss. This would cost about $5.70. Thus, the net would be a cost increase of 64 cents per year … I think you need to pick a new winner.”

Another figured the alcohol cost at $6 a year, and yet one more put it at $6.836.

Now this is a serious matter. Clearly, the gluttons for detail were unconvinced. So I spoke again with my champ of cheap. Happily, he had double-checked his calculations after being challenged on this very issue Tuesday by a talk-radio host from Melbourne, Australia.

The average floss sterilization takes not one-quarter of an ounce of alcohol but a mere one-quarter of a teaspoon, dribbled into his palm, he reported. With a pint going for 50 cents, not a dollar, his annual alcohol cost is a mere 48 cents.

“That bites into the savings a little bit,” he said, though it still leaves him $4.58 ahead of where he’d be following the floss manufacturer’s method.

Correction: The 48 cents worth of alcohol would bite into his savings if it weren’t for this: He uses the alcohol in his palm as a low-cost deodorant.

“There’s really nothing better to use,” he said. “It’s very effective.”

Consequently, he puts his alcohol cost for floss at zero.

“It’s absolutely a free ride,” he said.

Take that, all you naysayers.