We took turns in keeping mum occupied and she seemed to be on the verge of an orgasm nearly all the time. After about three hours we were extremely tired and mum looked like a limp wet rag, totally exhausted but with a great big grin on her face and seeming to glow with happiness. We had to help her up to the shower and we washed her down then took her to bed. She was asleep before her head touched the pillow. We noticed that even deeply asleep she had a huge grin on her face.
It was at this time that I realised mum had changed, she seemed to look younger, was visibly happier and friends and neighbours commented on it to me. She was not beyond ambushing me in the middle of the night with her mouth around my cock. I would get home feeling a bit randy and would come up behind her to cradle her lovely firm 36DD tits in my hands and within a minute I would be inside her shagging like fury. I was very lucky that I had a very high sex drive and seemed to be able to keep getting consecutive hardons with plenty of spunk to match.
We did that many more times over the years, John, Jan, Lin and I got a big house between us and were very happy, no-one needed to stray. Lin and I had three children and John and Jan had four. No need for baby sitters and each couple could go on holiday away from the kids. Of course the holidays with all twelve, including mum, were great, incredible fun. With a minimum of two salaries coming in there were no financial worries.