I've been using fletch tape exclusively since 1993. To the best of my memory I have never once had a feather come loose or fall off.
Once you get the hang of using it, you'll be able to fletch (and shoot) a half dozen arrows in about a half hour. I agree with the suggestion about putting a dab of fletch-tite glue at both ends of the feather. I suppose if I was going on a "hunt of a lifetime" and it REALLY mattered, I might consider running a bead of glue down one edge of the feather quill as an extra precaution. Really though, I think this is probably overkill. Speaking for myself personally, I feel that as a good guestimate, I waste about 1/8" of tape per feather. To be safe, you can figure on about 1/4" of waste per feather. Use this waste figure, the length of a roll of tape, the number of feathers per arrow (3 or 4 fletch) and the length of your feathers to establish a reasonable estimate as to how many arrows you should be able to fletch from single roll of tape.