The Bibba webinar I quoted (post 48) said after 15 complete brood cycles, cells are sufficiently reduced to affect the size of bee and the bee’s collection of pollen & nectar plus the space to store it. This was supported by the research I mentioned which studied comb from 1 to 6 years old and all the years in between. Concluded that comb 3 years old and above should be changed. Clearly comb that has just had food stores in could last longer vs comb in the centre of the nest
They also made the point, also made by post 53, that this would not occur in nature as the wax moth and mice would remove old comb and the colony would either build new in free space (usually above), or abscond, or swarm.
It’s only man who has confined bees to a box, leaving them with no option but
to use the comb they are given.