<<will mean a reduction in payments as these last years at zero will deduct from what had otherwise been maximum contributions for about 35 years.>>

SS uses your 35 highest years of earnings (after indexing those earnings for inflation). If you have exactly 35 years of posted earnings with SS, they will use all of those earnings and your benefits will not decrease. If you have less than 35 years of earnings, there will be some zero years added in to make up 35 years and benefits would be reduced because of it.

Continuing to work after having 35 years of earnings makes your monthly benefit higher (add in a high year, subtract a low year). Once you have the 35 years, it just means SS won't calculate benefits using zero years.