Absolutely, though I rather suspect that speciation would occur for the 'quick' variant of the species.
Take humanity as a case in point. We have differing reaction speeds. Some people live longer than others. Some take more time to grasp abstract concepts than others. Some are faster at mirroring bodily movements (dancers). It can be argued that we are this species with a much smaller variance in 'speed' and a much less well defined link between speed and lifespan.
Given that speed is inherited you're going to see one heck of an evolutionary pressure towards being fast. The slow will die a lot more than the fast unless there is some reason for the fast to take care of the slow. Perhaps the slower are treated as the best social historians or religious leaders, given their long lifespans. In an early society the slow will die out pretty quickly in the same way that those unsuited for survival in mankind's early history died out.
But even if the society takes care of the slow there is still going to be an evolutionary drive towards being fast. Notably that the fast reach sexual maturity, can reproduce, have children and die multiple times before the slow finish saying good morning. Why have a slow partner when you could go out and get a fast one?
This is why I suspect you'd rapidly get different species. The fast would pair off and breed with each other, the genetic differences in multiple generations of fasts building up until they are incapable of interbreeding with their slow relations. This wouldn't be a conscious thing, it's just that fast favouring fast will lead to fast being inherited, and since you can potentially have 100 generations of fast in a single generation of slow (and they're more adaptable) you'll need some reason to maintain interbreeding.
Perhaps the slow make for good partners because their long lifespans enable them to look after multiple generations of family. Perhaps they make good partners because they're all rich after a lifetime of inheriting successful fast spouse's assets. Perhaps again it's a religious thing, and having a child with a much slower partner is seen as sacred because it's written on a temple wall somewhere.
Please note that the answer above is taking the two extremes as a binary state (fast/slow) whereas the truth would be far more complex. The speeds would be a continuous distribution with more 'middle' people than either super fast or super slow, and the exact distribution of speeds would change along with generations, fashion, societal influences and political change.
So it's possible, but unless you put some other constraints in place it's unlikely to be stable.