Defects stay on your account for a year.
So, you rating will only improve if you sell a lot of items with no issues or they will expire in time.
Really, unless you are a business seller, being below standard doesn't matter a lot - in my opinion.
"There are two ways to be fooled. One is to believe what isn't true; the other is to refuse to believe what is true.”
Søren Kierkegaard, Danish philosopher (1813 - 1855)
