So how often should i have anal sex with my wife, if not daily?

For sure not daily, once in a while is okay if your wife also enjoys it because frequent anal sex may cause deleterious health effect to your wife.

Its entirely between you two and needs no advice from anyone else

Agree with Dr. Le. Anus and rectum are not designed for sex. Anal sex is likely to damage the anal sphincter and could lead to fecal incontinence.