I took my SS at 66 on my husband's account. He is 77 and has been collecting since he was 64 due to health reasons. I believe they awarded me half of what would have been his full retirement since I filed at full retirement age. I will be switching at 70 to my own. These last four years of work have been my highest ever - three, sometime 5 times what I ever made in any year. I know my amount will rise 8% each year; but could it rise more due to my earnings?
Sure. The calculation of your base retirement benefit rate, or PIA, is separate from the 8% per year increases that result from delayed retirement credits (https://www.ssa.gov/planners/retire/delayret.html). When you file for your retirement benefits, Social Security will first calculate your PIA based on your highest 35 years of earnings adjusted for wage inflation (https://www.ssa.gov/pubs/EN-05-10070.pdf). They will then increase that amount by 32% (i.e. PIA x 1.32) assuming that you wait until age 70 to start drawing your retirement benefits.