The limit is that a route may not have more that 255 directional points (including the route points) in one route.
If it's more, a zumo will notify that the route cannot be calculated completely, etc etc.. (not important for the question)
BUT! In BaseCamp I have no idea how much directional or route points there are in a route. Nowhere is shown the amount of these points.
It would be very nice to know the amount of directional points in the next (beta) release.
In the below picture i have used the amount route points in the route name, so it seems to show, but is only a part of the route name.