I'd like to note that I get all of my 20 requests every day, as I am my only neighbors(I have around 30 accounts) and I request from the plot I'm expanding from. So that theory doesn't hold. When I'm close to expanding(5-10 away from 60) and I send out requests, I switch to my other accounts and answer my requests, but often I will stop midway through when I have just enough for the expansion. I go back to my main and expand. Then later in the day when I feel like it, I finish cycling through the rest of the accounts to answer the rest of my requests. And I always get all of them.