Interesting question indeed.

By OzzyKP
I think so, for the purposes of fantasy games, people need to consider different factors related to race. Many of the fantasy races have much longer life spans than humans, yet typically lower populations. I think the general assumption is the other races have lower birth rates.
I only can add a biologist point of view here. What is generally observed (without considering external events such as diseases, war, access to a good healthcare, etc.) is a kind of rule like : "the more an organism has a big lifespan, the more it tends to have a long childhood status, big needs and a low fertility/birth rate".

Human is a kind of a "super predator" in our world, with a long lifespan, a long childhood and a low birthrate. On the contrary, a lot of insects or small organisms have a short lifespan but multiplies quickly. And, yes, there's often (but not necessarily) a correlation between size and lifespan.