I think the frogs can be fed right up until the time they start seeking a place to hibernate. They don't have the same digestive system that fish have. Never seen any frogs come up to be fed like that. I bet that's so cute!

Some of the hand feeders.
http://i1222.photobucket.com/albums/dd492/barkingspaniel/Handfedfrogs.jpg

Here they are.

Here is a link that might be useful:

Good picture of the frogs, but I really want to know the story of the red chairs on the tree.

DonaldB,

My frogs, too, come up to me to get fed. They swim over from the far side of the pond, then they sit on the rocks and stare at me. Very creepy as they don't blink! Sometimes they get overexcited and leap at my fingers just as I'm reaching down with the "worm".

Now, since I HATED giving them live worms I came up with an idea that has worked out fabulously. I cut up hotdogs into long, thin pieces. I put these pieces on the end of a stick and watch the feeding frenzy. There doesn't seem to be a health issue using hotdogs as I did this all summer and never saw sick frogs. Just BIG, FAT, ones!

mondotomhead,
I'll have to gtry your hot dog way of feeding next spring.
We usually get crickets and "super worms" at our local Pets R Us in Auburn and they have a blast. Hope the eight we had this past year are "bedded down" in some safe and comfortable spot for our upcoming Massachusetts winter. We never have good luck with them surviving past winters no matter what we provide.
Stay warm.