Yes, the bacteria has to be fed, and there is WAY more bacteria present in the "dose" you give your tank than is necessary, and some does indeed die off, so that is why you don't add a couple of fish with a full dose of the product, because you are wasting money. Also, quite often you want to stock your tank fully so that the territories are chosen at the same time, and you are not trying to add additional individuals after the territories are staked out, or you want to purchase a fish that prefers larger groups, but without BioSpira you are reluctant to add your full school at once. If you add your fish slowly, you might as well be doing a fishy cycle. If you use BioSpira you can stock your tank just as you want it to be, and allow all of the fish to grow up together, which I think is a good thing in many cases. If you do want to add fish slowly, add the BioSpira slowly along with the fish. It keeps in the fridge, and it prevents overtaxing your biofilter.
As for beginners, I think they should do a fishy or fishless cycle anyway, keeping track of their water parameters, and grow their own biofilter so they can validate the process in their minds and understand what is going on. So many beginners have not an inkling of why they have all of the common problems with new tanks, like cloudy water and fish deaths, and if they understood the nitrification process it would help them immensely. This stuff is not a requirement for good fishkeeping by any means, as you can quite easily manage the biofilter the tried and true way, but it does what it says it will do.
A big thank you to Tankgirl 
