Dry yeast

The last few brews I've done I've mixed either Safale 04 or 05 with Coopers brewers yeast (an amber, an outmeal stout, and a black IPA). I've had great results. Today I brewed a porter and threw some Windsor and Safale 05 on top. Am I really using two yeasts, or do you think one just takes over from the beginning?

I'm scared to stop using two yeasts as my results have been outstanding.

What do you all think?

don't be afraid. most of us use only one yeast with equally good results. chances are both your yeast and doing their job and melding their results as best they can.

One yeast will work just fine, but, do whatever you want if it's working for you.