On the Level – Eskimo - Cocos2d-x by Example Beginner's Guide - page 336

Loading the level data
In Eskimo, since I only have five levels, I chose to have one .plist file that contains all
levels. This may not be the best option in a larger game.
Although Apple devices will load and parse the .plist files quickly, the same may not
be true for other targets. So limit the size of your .plist files by organizing the data into
multiple files. You've probably seen games that divide their levels into multiple groups or
packs. This is a simple way to create an extra preloading screen your game can use to parse
level data. This can also be used as a means to keep file sizes to a minimum.
In Eskimo, we could have the .plist files containing 10 levels each, for instance, and
then 10 groups of these, totaling 100 levels.
So it's time to load our .plist file and parse the data for our levels.