Mickey2...I think worms reproduce at a certain rate, depending on conditions. I am not sure why AbbeysDad uses that feed..(but I am sure he will inform us..at least I hope he will). I have experimented with it, just to perhaps entice some fishermen to set up bins, reduce their food waste and have free bait. My goal in doing vermicomposting is to reduce the amount of waste generated by my family, so I do not buy stuff to put in my bins.
I think a worm's life expectancy is maybe 4 years in a bin, under the best of circumstances. Their lives are much shorter outdoors, in the ground, as there are more predators and weather to contend with.

Lured by the promise that vermicompost is an even more nutrient rich and biologically active organic fertilizer than regular compost, I have two objectives: The short term objective is to produce a lot of worms - my long term objective is to produce a lot of high quality vermicompost...1) An indoor system capable of processing all (or nearly all) kitchen waste and 2) a larger scale outdoor system to process compostables of grass clippings, hay, leaves and some manure. (I garden organically in about 3000 sq. ft.)
Obviously it's winter here in CNY, so the current focus is building the herd in the basement.
The corn meal, bran, alfalfa pellets, bread crumbs etc. simply augment the kitchen waste to provide more balance in the food stock which I believe will help in producing stocky, robust and more prolific worms. There is no real recipe. These materials just serve to stimulate the bin bio culture. I most often add these dry ingredients to offset very soupy stocks like processed fruit.

YOU DO NOT have to feed your worms anything other than kitchen waste. After all, redworms do very well in compost and manure piles - in addition to proper temperature, moisture, suitable bedding - bountiful decaying organic matter is all that is necessary in order to create worm heaven.

I don't know if these food supplements truly promote larger or more prolific worms, but I believe they do not hurt and these additives would seem to provide a more balanced diet and are very inexpensive.

Yes, the corn meal I use is the same that you'd buy in the grocery store to make corn muffins.

4 years is probably a good average although I have read that some researchers believe that well cared for worms could live 10 years or longer.