Have you tried playing with yourself, spanking the monkey before having sex with your wife? Or ask your wife to get you off with oral sex?
This will normally de-sensitize the penis so you will last much longer.
It has been proven that 70% of women can't get to ogasm from intercourse at all, regardless of how long you do it. Their clitoris must be manually stimulated with a good lubricant to get their wall shaking ogasm. Once she has already had her ogasm, then you getting off prematurely will no longer be a problem for her.