I feed Primal, Stella & Chewy's (both frozen & freeze dried versions). They eat every meal like it was their 1st time trying it, totally love it! For age, the store bought premade raw foods are all nutritionally balanced for all ages, except for the 'supplemental feeding' products.
For treats, they get ZiwiPeak (lamb), sometimes different proteins like fresh poached wild salmon or boiled chicken, some fruits & veggies if I happen to have it.
For my guys, they didn't do well when I mixed kibble & raw food (but every dog is different). They got digestive issues, like gas & loose stool.
Here's an excellent video by Dr. Becker (3 part video), she talks about the "digestive confusion" @ 2:30