I'm a little confused about progenoid glands in the space marine background.
Their stated purpose is to create the material (geneseed) required to produce more space marine organs, once havested. Each of the two (neck and chest) progenoids takes 5 and 10 years (resepectively) to mature. After which time, they can be removed, but the chest one is typically not removed until the death of the marine.
The progenoid material is then used to grow more organs in vitro. Including more progenoid glands.
Here's my confusion. Do each mature progenoid only produce one of each of the 19 implants (including 2 new progenoid glands?). Or can the produce an indefinite number of them (over time)... in which case why bother harvesting when one could have a store of them all pumping out organs all the time. And: can a harvested progenoid gland/s be re-implanted in to a new recruit (i.e. recycled), or is a new one required?
The answer to the above questions affects how long it would take a chapter / legion to re-populate itself, but I'm still a bit confused!