"Outlet" Lucky Packs?

I've been hoping to finally snag my first lucky pack this summer, and to prep, I've searched the various resources available on lj. However, there's one thing that's throwing me off because it either means it's not done very often or people don't really write about it or both.
How many LPs are released in a season? Sometimes I see "outlet" or b-grade packs Put on sites like Innocent World, when they already offered a smaller, but I assume, higher grade lp just two or three months before. Is this the norm? I've seen it happen for both winter and summer, but I'm not sure that it's a consistant event. I'm new to buying lucky packs, so I don't know exactly what to expect in the coming months.