I will admit you are losing me with the thought that booking less than 7 days initially reduces the chance of getting the reservation initially. Whether booking 5 nights or 7 nights no one starts further than 11 months out.
Throwing walking out of the equation, for example, I want Dec 1-4 and another owner wants Dec 1-7th. Both of us will book on January 1st.
Now, say both of us actually want different dates - I want Dec 11-14th and they want Dec 11-17th. We both can start walking on the same date, and I'll use the Dec 1st booking (but yes, it is key to pick a day to actually get it started and this day could be way back in November if necessary or even further but we both would be right at the 11 month window, whatever that date is, to start). Since I'm walking with fewer nights I need to call and modify my dates on Jan 4 to Dec 4-7th and the other owner doesn't need to call until Dec 7th and will change to Dec 7-13th. On the 7th I have to make my second call and would modify to Dec 7-10th. Then I'd make my third call on Jan 10th to modify to Dec 10-13th. One day later I could call and have my Dec 11-14th dates (4 calls total to modify). And on that same date the other owner would make their second call to modify and finish their walk with their Dec 11-17th dates. The owner walking 7 nights had no advantage over me in starting the walk though.