Originally Posted by YoshiEnVerde

Pie Timers seem to reset exactly 24hs after the Pie was given... You have to take care on when you give them, or you'll lose some possible pies one day

What Yoshi said.

If you have trouble finding friends to chuck pies at, the next alternative is to hit up friends of friends (of friends of friends of fri...you get the picture) that aren't directly friended to you and just keep chucking pies until the mission's done.

Instead of hitting the "Tease" button under a friend avatar, click the avatar itself and it will take you to the friend's page. From there you can see and choose from that friend's list of friends, and do that repeatedly until you find people unrelated to yourself to pie up.