I dig my fall crocus up, split and replant every two years. I plant them 4-6 inches deep. I notice every second year the bulbs, which have grown to baseball size, are protruding out of the ground. Did I not plant them deep enough two years earlier or are they telling me it's time to dig and split them? Also, when is the best time to split them? I have done it both after the foliage dies back in June and after they bloom in Sept., doesn't seem to make much difference.
This article has some interesting information on autumn crocus. https://www.gardeningknowhow.com/ornamental/bulbs/crocus/autumn-crocus-growing.htm
The corms' protruding out of the ground is telling you it's time to divide and conquer.