agreed.. the brake master cylinder can be thought of as a large plunger with a few rubber rings around it.. If not used for a long while those rings dry out, crack or don't hold seal properly. When you go to bleed them they fail and your left w/o brakes.. Thats why some mechanics, while bleeding the brakes, place a block of wood under the break peddle. To stop the peddle from hitting the floor and pushing the plunger in the BMC to its furthest position, if it hasn't been done for a very long time.
Happened to me.. put on a new BMC and that should solve you're problem. If you had a leaky caliper or something, you would see signs of it on your rims. If you had a leaky line some place. probably see it on the garage floor.
Indeed on bench bleeding. here's my thread on me bumbling my way through it..
http://www.toyota-supra.info/forums/...-brakes-2.html