Actually I see banknotes and coins to be two different things, especially when it comes down to MAINTAINING them!
Banknotes in my opinions are all unique because of the serial numbers and is easily identifiable. (except for some printing press hiccups and print the same serial numbers) On the other hand, coins are pretty much difficult to tell apart unless you start to go into details, like scratches on the head, die clashes, inique features, but this almost difficult to do so on freshly minted coins, unless they all get slabbed and given unique IDs.
I personally find maintaining banknotes to be very difficult. Firstly, if one accidently stored them in PVC folders, well for coins you have acetone, but there isn't a solution for banknotes!

Banknotes are fairly sensitive to folds etc, and to protect a banknote, well it's long, thin, and has to be stored in a flat place doesn't it?
And lastly, coins and banknotes are two different objects! One's generally struck in metal and the other is printed on paper. And for such, storage is two amazingly different story. My coin collection usually has some sort of silica gel packs but for the banknotes, I have to watch out how dry it gets, else the paper will start to crumble!