I decided no more for us at 35/45. There had been a change in DH's energy level from baby#1 at 30/40, and we had baby#2 at 32/42. Realisticly, I would have ended up doing a lot more donkey work for a 3rd child, plus I had form for tough pregnancies and births and decided I wasn't going to write off a third year of my life on pregnancy/ recovery from birth.
By co-incidence DH was the same age as my "dad" (my young grandparents raised me). He was dead at 53, before I went to secondary school. Admittedly DH looks after himself better, but now in his late 40s, he's the same age as my dad was when he had his first heart attack.
When "DM" was 60, she did childcare for my considerably younger sibling (I was in sixth form). She was very energetic and sociable, but it was still draining to her. A few years later, the arthritis really struck and impaired her mobility considerably. Thank goodness she wasn't having to run around after primary school children at that age. In our case DS1 has high functioning SNs that have become apparent over time. In some ways he's an easy child. In other ways it's draining, especially emotionally.
Our parents/ grandparents are in their 80s and while they are on good form, better than average, the niggles are catching up, and their worlds are contracting. They don't hold much interest in our lives and the DCs. With one grandparent, age has meant that our DCs really don't have the two-way relationship that all their cousins did before, even the ones a few years older who live a similar distance away.
There isn't a right or wrong limit on when to stop having children, other than biology which does on average kick in for women in a timely way. It is very personal. I have no regrets about stopping when we did and I came very close to TTC for #3. I would worry about a mother on the late end of her fertile phase with a much older man though. It's a tough combination and the odds get high for the enjoyment of parenthood and the child's quality of life being impaired by health concerns.