IPhone – Synchronize with Google+ Photos

As you have figured out, you need to select fewer folders/photos in order to keep it from failing. Simply compare the size of the folder(s) you want to sync with the space available on your iPod.

On a Mac, you can select a folder and press command+i (or control+click and select Get Info) to display the size of a folder.

On Windows, you can right click and select Properties to display the size of the folder.

Google + for iOS, Google Photos for iOS and Google Photo Autobackup do that. The age of the pictures is not really relevant, because the last app would upload any image on your computer (on the pictures folders mostly). Also, Picasa used to be able to sync your pics with G+, although I'm not sure it was automatic.