They can go a while but you really need to watch the weight. If you see it dropping then you need to get involved.

I feed my crickets in a bowl. Just place a smooth regular round bowl in and drop a few crickets into the bowl. The round smooth sides and bottom don't provide traction and the crickets can;t climb or jump out.

Some folks use a clear bowl and sink in down into the substrate so it will also catch any loose crickets that are roaming the tank.

In the morning, just dump the remaining crickets back into the cricket keeper for the next feeding.
Once your frogs become use to you the calc covered crickets will disappear just like the non-covered ones :-)