It's strange, isn't it. I bet if you asked todays mothers with small children if, when their child raising days were over and the last child had just left home, they would be prepared to start all over again with child care every day, the answer would be a resounding NO!
The grandparent army - yes, it's an army of pensioners - offering free childcare is a recent phenomena. Go to any park, supermarket or garden centre mid week and there is a host of older people pushing buggies and supervising young ones. Many look worn out. We've been there ourselves and chatted with other grandparents as we've pushed swings, chased little ones around and lifted them up and down off play equipment.
The love is obviously there, but in many cases the stamina is lacking and the enthusiasm for being in charge day after day has waned.
We get one life and there is a reason our bodies reproductive system pack up when they do. I know the world has changed, but older people remain older people with less energy, and continuous child-care may be a privilege and may indicate trustworthiness, but it's also a thief of hard-earned leisure time, when there is less of it in front of us to enjoy. The clock is ticking.