I'm not sure about this limited hair cycle theory.
The number of hair cycles can be increased with minoxidil, finasteride and other hair loss medication, otherwise people would never see any regrowth, and this makes the limited hair cycle theory completly void.
A hair follicle sensitive to DHT will progressively shrink until it becomes a vellus hair, but it can happen in three years (some people get bald only a few years after they hit puberty, has their hair experienced 20 hair cycles in such a short time ? Of course not).
A healthy hair grows, a not so healthy hair does not.
The anagen phase of a healthy hair follicle lasts 3-4 years, so a new hair will sprout approximately every 4 years. We supposedly have 25 hair cycles, making it enough for a lifetime, but we can only imagine it works like that. I haven't seen any study proving that after 25 hair cycles, hair growth suddenly stops, 25 is an approximation, it can be 5, it can be 50, the only limit is when the hair follicle is not healthy enough to produce a new hair.
In short, 25 hair cycles is the right amout we should have for our hair to last a lifetime, not the ACTUAL number of cycles everyone has.