You shouldn't start a race against the clock
Yes. You aren't incorrect regarding this. Everything will come on time. We just need to put our efforts. However, We shouldn't just sit idle and hope that all will take place automatically.
There is one tangent though. In facts, having 5 kids in 25 and 5 kids in 40 have some advantages and disadvantages. One of the advantages of having 5 kids in 25 is there will be enough time to raise them. Disadvantages (maybe) are financial issues. However, those people with average life expectancy is 60 - 65 years, having 5 kids at 40 may become problematic in term of "not having enough time to raise the kids".
That's my thoughts.