I would say you know you are co-washing too much when you are getting excessive buildup in a really short amount of time but not all conditioners are created equal so some conditioners you might be able to use more often without having much of a problem.
Also, take into consideration how much or what kind of products you are using on your hair in-between washes. Since washing with conditioner is not as powerful or cleansing as shampooing you don't want to go crazy with styling products and such because the conditioner is not going to get your hair as clean.
I don't cowash more than 1 time a week because I work out but I also shampoo once a week too. I have natural kinky-coily hair so I personally don't think it would be wise for me to wash everyday because I like to have detangled hair whenever I do.
I say try it and if it's too much, and I'm sure you'll know if it is, then go back to what you were doing before.
Hopefully, somewhere in that rambling there is something that can help you.