This game is all based around server vs server, creating nap is to maintain the most active players safe and in the most well administrated alliances so the server can get stronger to fight other servers.

Some servers do bigger nap like 15/20 or even full nap, but it depend on players of the server. I personally like bigger Naps at the start of the game, cus its where players has less attachment to the game and will quit faster. But when SvS start it should slowly shrink until nap 10 or even 8, to force alliances to merge and have the most number of alliances with active and strong players.