I have read through a lot of the memory maker threads but I want to totally understand the way it works. If I advance purchase a memory maker, it isn't linked to my check in date, right? i have split stay with back to back reservations in November this year. First reservation is 3 days room only. The second is a package for 4 days which is where I am eligible to advance purchase. If I advance purchase on the second reservation, I can still activate it on day one of the vacation? it wont make me wait until the second check-in day?
Memory Maker isn't linked to your onsite stay at all. You don't even need to have an onsite stay to use Memory Maker.
You can advance purchase Memory Maker, at least 3 days before the first day of your 3 day room only stay. It could be MORE than 3 days before, that doesn't matter, you could advance purchase it a month, or more before the first day of your 3 day room only stay.
When you go to the parks, you start getting pictures taken. Each picture will go into your Photopass account, and will remain there for 45 days. This happens even if your do NOT have a Memory Maker. After you download your first photo using Memory Maker, you then have 30 more days to add additional photos to your account.
Since your trip is only 7 days, this limit won't matter to you.
Make your advance purchase at any time. Get photos taken at the parks, you don't need to do anything to activate Memory Maker before getting photos taken. Once your trip is over, go to the photopass section of My Disney Experience, and edit your photos as you see fit, then download them. Just make sure you finish your editing, and download your photos within 45 days of the day you have your first photo taken.