Google Photos app offers to backup our photos for free, in their full resolution using your google combined storage (Gmail+Docs+Photos up to 15Gb free), or at 'High quality' (up to 16 Mp photos and HD videos) without affecting your quota.
I think that 16Mp is pretty much good for a long term backup (in fact I thought that 8Mp was very good), so I go for the 'High quality' option, bu it led me to two main problems:
As long as Google is not backing up my full resolution Photos, the auto delete feature is unavaliable.
Sometimes in the past, my app had switched to full resolution backup, without any advice, and some of my files were backed up in full res taking part of my quota away.
To try to solve this, I wanna greate a script, Python/Perl may be good picks, that find those high res images in Google Photos, download/delete them, and push them to the backup again using the free storage 'High quality' mode.
TL;DR
A little more context, I am a freakin' father that take photos always at burst mode from my kid, my pets, special family momments, etc. So it is not surprising that Google should not be happy in backing up all those images.
Beside that, my Full Resolution Photos are not that big at all, most of them never got to that 8Mp point, but if you use the original/full res backup mode they will take space from your gmail/drive account.
Setting up a seccond, tird, n-th acount seems to not work so well, cause you will need to switch among them to search or find the great creations they do with our photos.
Just found a better way, going to your Google Photos web interface you will find a RECOVER STORAGE option, it will try to convert all your previously uploaded photos to High quality, which means they will no longer count against your quota