We don't full time but we do have 6 grandkids from 5 to 18 and we're very involved in their lives, but we're NOT parents again. They all live within a couple miles, one lives within a couple hundred feet.
We go to concerts, sports events, plays, etc. Sometimes we provide transportation when siblings need to be at opposite ends of town.
At one time two of them lived next door; that had it's moments for sure. Some funny, some not.
Three of them moved 135 miles away to live with their Dad a couple years ago. DW was heartbroken but it was best for THEM. When the weather was snowy I'd sometimes take the 4x4 to pick them up for the weekends with mom. Because I wanted to, not because I was expected to.
DW does make lunches and takes the one who lives down the street to school every day. That's a choice she made though, not one that was thrust upon her.
I went on the obligatory middle school Washington DC trip with the oldest one (she asked me to go!) and we had a ball.
I wouldn't trade it for the world.
That said . . . I'm a military brat. We moved every 3-4 years, often from one end of the country to the other. That meant we didn't see our grandparents every month, or weekend, or sometimes year. But we did visit and we did have a great time when we could get together. Was I as close to them as my cousin whose Mom's house they snowbirded at in the winter? No, but I know they loved me and were proud of me.
What I'm saying is different strokes for different folks, but the most important thing is to spend quality time when you can, love them, and let them know that you do. :)