Haha, I only had the one dc so not at all tired of parenting... unlike my poor namesake!
People are of course free to do whatever they want to do, but I guess I just don't see a conflict between grandparents helping out on a regular basis and having "their own lives" - I'm certainly not suggesting that they should be providing childcare all day, every day, or that they should never be allowed a holiday etc, so they should have plenty of time for other things. But my dc - and any future grandchildren - will always be a big part of "my own life" and I wouldn't want it any other way.
As a parent, I never had any expectation of regular help from my parents as it simply hadn't occurred to me that this would be possible - we didn't live near enough for a start. However, once dd was born, they were completely besotted and chose to move much closer to us so that they could have more time with her. They picked her up from school twice a week, fed her and drove her to her extracurricular activities. I saw how much pleasure and joy they gained from the relationship and I saw how the strength of their early bond carried through as they - and she - got older. I guess I can't really understand why anyone wouldn't want that if everything else aligned.
I've spent a lot of time around older people lately, for various reasons, and I see the tremendous difference that really strong family bonds make in those later years. Those bonds don't just happen by accident - they happen as the result of ongoing investment in relationships over an extended period of time. I honestly can't think of anything that I might want to be doing in my later years that could possibly be more important than supporting and spending time with the people I love. Not to the exclusion of other interests and priorities, of course, but certainly as a key feature.
Perhaps people's views on this depend on how they have experienced parenting? I have always loved being a mum, and haven't found that it has prevented me from living a full life of my own - I've had a rewarding and successful career, I've studied, I've volunteered, I've travelled, I've pursued my own interests. I have a happy marriage and strong friendships etc. I've always felt that I've had my own life while being a parent, so can't see why I couldn't do the same while being an involved and helpful grandparent?