Are the skins available as long as the October bundles?

Hey guys,

I've seen that with the October bundles, certain old skins are available for Champions as well (i.e. Pirate Ryze).

For how long are they available (I mean the skins separately from bundles) and is it possible that they might be part of weekly discounts (50%)?

I'm sorry if the answer has already been answered before. I'm a new player and I can't find it.