Leopard geckos do not have growth spurts in my experience, they should steadily grow and shed until full size is reached. You should have been feeding them daily until they reach sub adult stage, then possibly move to every other day or keep it up depending on the conditions and the matterism of the gecko in question. My last leo loved to eat and ate everyday until 8 months of age when she hit adult length. If the gecko does not get enough food during the early growth phase it is likely to turn out a small adult and not be as long or wide as it would have been with proper nutrition.
The gecko should be allowed to eat as many crickets as they can catch in a reasonable length of time. Any additional left over crickets should be removed as to not stress the young gecko. This is a better gage of how many crickets to feed and avoids over and under feeding. The proper size is based on the head of the gecko in question. This information is readily available on caresheets and care books, which I highly recommend for anyone caring for any reptile.
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0.1 Albino Leo Gecko
0.1 Crested Gecko
1.0 Dear Boyfriend
Departed: Harvey and Spock