No, no it's not.
You only get feathers for subscription from the friend who subs the longest. So if you have two friends, and one subs for 30 days and the other subs for 240, you only get feathers for the friend who subbed 240. You don't get more feathers for the 30 days your other friend subbed.
Now, if the friend who subbed 240 quit but the friend who originally only subbed 30 came back and resubbed for an additional 240 days (totaling 270) then you would get the extra 5 feathers.
EDIT: You would get a bonus 5 feathers simply from recruiting a second friend, however.
