Do you have to be logged in to play the games or are they available offline (without internet connection)? For example - a household has two PS3's, each with their own PSN account. One PSN account is also a PS+ member. Would that member be able to install the same games on both consoles (multiple download) and if so, would the non-PS+ account be able to access those games? Does this make sense?
AFAIK, it is dependant on the game in question, but for most, you only need to be logged in for the initial purchase.
To play on multiple consoles, you will need to have the account that has that PSN+ subscription on both machines, so that the console can download, authorise first time etc, but not necessarily logged in to play - this is also game dependant, most games I've seen allow it to run on up to 5 consoles.
A few games allow on machine to run the game and/or you have to be logged in to play, such as Final Fight (Crapcom those bas
tards)
Any PSN+ discounted games that you buy, as in, you spent more that R0.00 to get them, will be yours to keep even if you cancel your PSN+ subscription. Any games that you get for free will be de activated if you cancel your PSN+ subscription (they all get reactivated if you activate your subscription again later on)
Also take note that some free games are removed from the free collection to make room for new free games, therefore, you should complete your "purchase" of those games while they are free, even if you are not downloading them right away.