In terms of your thinking out loud about whether to try to manipulate the timing of when you get a vaccine dose, there are so many potential factors, lots of luck is involved, and there are no guarantees that what you and authorities will eventually discover will tell you that you were right to delay, it might just as likely reveal that you should have got another vaccine ASAP. And certain things might be revealed that the authorities wont be able to act upon during that vacination cycle anyway, eg if it turns out that a different sort of vaccine would be better, but it wont be available in time to protect masses of people against that wave. Or things that are down to random chance, such as if various different types of vaccines are in the system at the same time, but you have no choice as to which one happens to be available at the vaccination centre you happen to attend on a particular day.
I'm a simple case of a middle aged person whose only been offered 3 doses so far. I may as well describe what happened to me in terms of luck and timing for those first three doses, as just one example of how this stuff can play out:
I dragged my heels a bit when it came to booking first vaccine, because I was keen for more nerdy detail to emerge, and because I could effectively hide from the virus in the meantime, and could avoid being a potential vector of transmission to any relatives that were more at risk than me. That initial deliberate delay of some weeks happened to, by chance, enable me to end up getting a dose of Pfizer rather than Oxford Astrazenica. But this wasnt planned, it just turned out that way because by the time I booked my first vaccination they had decided not to give the Oxford vaccine to people a bit younger than me, and people in that age group were allowed to book fro the very first time on the very same day I happened to finally get round to booking.
By the time I could get my second dose, there was some early evidence that perhaps quite a long gap between first two doses had benefits for the amount of protection that may be afforded. So I was going to wait the fill 12 weeks. But then some things happened which made the authorities reduce that gap, and there were concerns about a resurgence in the virus, so I decided to go along with that and reduce the gap.
The same thing happened with my third dose. I was going to leave the full gap, especially as I still wasnt exposing myself to risky situations. But then concerns about Omicron loomed large on the authorities radar, and I decided to do what they wanted and get my third dose in December rather than dragging things out till early the next February.
Timing issues that I had relatively little control over for all 3 of those doses is that my periods of theoretical best protection were out of sync with other family members due to differences in age and medical conditions between us. eg my parents and brother were eligible for vaccination far ahead of me, so by the time I got a dose they had already entered a period where waning concerns had grown. Hopefully this was more of an issue for first few doses, and magnitude of potential waning/differences in protection against severe disease and eath isnt as great once 2+1 doses were done, but cannot really be sure that we'll never end up totally out of sync in a way that has significant implications ever again. Although as the authorities plan currently stands, I dont get another dose this winter and the rest of them do, and if this plan sticks then we wont find out if this plan had any big mistakes in it for some time, will either find out with much hindsight or they will get clues that make them change the plan (eg age cutoff) again at some point.
When making those latter timing decisions I had to balance various things including optimal protection, protection timing compared to next wave timing, timing the authorities preferred, ease of availability of booking slots and vaccine system capacity, what timing seemed like the best for broader society, what timing my family preferred. And people sometimes have other practical timing considerations too, eg having particular events on the calendar for which they didnt want to be suffering any post-vaccination symptoms, or wanted to feel like they were most protected for.
