When we went on our hike during the last week of September, we did not see any blueberries, which are more commonly found in August. So I learned that you have to know not only where to look, but also when to look!
Despite the fact that Finns like to go berry picking quite a lot, I do not think we need to be worried about running out of berries. There seem to be plenty to go around! Berries are intended to be eaten by local wildlife, in order to spread seeds to plant more berries. In this case, I suspect that some of the local rabbits and squirrels also take their fair share of berries, which keeps the berry bush population pretty healthy.
