I understand that all too well, the impatience with seedlings.
I'm afraid it does depend on species. Some grow quickly, others really rather slowly. Some of the slow ones are also small ones, so it is often difficult to see them developing. If they are green blobs, then they would seem to be fine, and you jus thave to let them go at their own speed. A good magnifying glass might help you see the young spines starting to develop though...
But I'd expect to see some first spines on a number of species at about 8 weeks, som esooner, some a lot later.