Nightcrawlers are not found everywhere. For example, i grew up in a town of 250 in southern Illinois. We did not have them in my yard or any of the other yards on our block, yet my grandmother's yard on the next block was full of them. Dunno why that is the case, but i am sure a soil scientist can explain.
Sounds like you are looking at the right times, you just need to find the right place.