Umm. I can honestly say it's okay to fill up one's storage on a mobile device with whatever is desired. This is 2015, just another year in the history of discovering how many things one can do with small computing devices. The cloud and streaming both make a big difference in how a lot of people look at storage requirements these days.
As far as photos go, I don't keep many on my iPhone past whatever I shot most recently. Generally I unload them to a laptop, back them up and then delete them from the iPhone.
I'd much rather have a few movies and a couple hundred tracks of music on the phone rather than a zillion photos. But that's probably because a lot of my photos are of fabrics and have no earthly purpose short of going into assorted quilting-project folders that live on my laptop.
When it ocmes to the larger iPad though, I'm not happy with small storage. I like to keep back issues of magazines along with lots of movies, video podcasts, TV shows and some apps that have sizeable chunks of data.
With the smaller mobiles like an iPod touch, I'm more than content with 32GB now, and can even see getting my next iPhone with only 16GB. Traveling light gets easier with the option to let purchases live in the cloud until wanted locally.