SW is right, as I have 77 neighbors on my 2tina account, and two days ago I sent out a request asking for 50 of Thomas Library Records (Incubation Plans), to ALL my neighbors, knowing full well that not all my neighbors would see the request that day, as only 20 can answer it. When I logged into my game yesterday, another 20 had replied (and I hadn't sent out anymore requests), as I knew that after the first day and those first 20 were answered, my original request would then be sent to another 20 of my neighbors. I just logged into my game and another 8 have been answered, so I'm only waiting on 2 more requests to be answered.
Since I didn't send out any requests, other than the original, my backlog for this request will most likely be 3 days when the next set received it. However, I'm not a patient person so decided to just ASK my queentina3 game and Stormie to answer those last 2 needed requests. It actually went through and from my queentina3 account, I answered the request.
The people you're getting requests from 7 days later probably continued to send out a request to their neighbors EVERY DAY which is causing the backlog of a week.
I've very rarely send to all my neighbors, but knowing I needed 50, and that it would be days before I'd even have to worry about requesting anything else, I went for it and sent to all my neighbors knowing I wouldn't backlog my system by more than a day. By tomorrow I could send out more requests and 20 of my neighbors would get them, but I won't have anything to request just yet, and that is why I did it.
I do hope that makes sense. I haven't had my morning cup of coffee yet.