I only request 20 maps each day because that's the maximum I can receive. I have read that extra requests will be held until the next day and then sent out but that's not my experience and besides it puts the amount of maps I'll be receiving out of my control.
So if I'm in the middle of an expansion, then I go to my arctic isles where I CAN request maps. It's the only reason I go to arctic isles.
And here's where I like to be in control of how many maps are coming out. I don't want to squander valuable maps on expanding my arctic isle. So if I have say 60 out of 64 maps I request only 4 maps. 5 at the most. Then when I go to arctic isles I won't have enough to expand there (I think I only need 9 there) then I can ask 20 of my neighbours.
By the following day I will be able to start expanding another block on my main isle.
Don't forget that at 64 maps and only receiving 20 a day that's more than 3 days worth and less than 4.
I'm level 81