I'm 51, my wife is 52, we've had two kids together one is 22 and the other is 19.
We've been together for 26 years and have been married for a bit over 23½ years.
My wife usually initiates sex about a ⅓ of the time. I get turned down, I don't know? Maybe around once every 12-15x that I initiate.
We share sex together usually at around 24-32x a month, yet there are still times when it is a bit more often.
That said, knowing how much sex other couples share, is unlikely to make any difference to how much you and your wife share.