Keeping basic land

I've had a bit of a love/hate relationship with basic land. I love seeing the different artwork in many of the editions, but from opening so many boosters, Intro packs, Fat Packs, and other product I have accumulated far more than is useful (as a player).

So, as a player, I've stopped opening those land packs in the Fat Packs and have simply sleeved 30 of each type of basic land.  I insert the requisite quantity into whatever deck I'm playing at the moment.  It reduces the number of playable sleeves I need to keep, and it simplifies what I do with new land that comes in: it goes into a box, whether singles or packaged lots from Fat Packs, etc.  The foils, and any full-art land go right into my trade binder.

As a collector, however, I really want to collect full sets of land from each block. If you were collecting land,

1.  How many of each variant would you keep? One? Four? More?

2.  How would you store them? I'm assuming penny sleeves would be in order, or is even that overkill? After that, just sort them and store them in boxes?

3.  Is there any evidence that full block collections have more or less value based on whether or not they have a full quantity of the block's basic lands?