I used it and ran out. I only did a little at a time. Like you 1:1. I need to get some more but I have this big acan of spray. You can buy smaller spray cans like at some beauty supplies or dollar store. I just give the bottle a good shake any time I mix it. That way no waste. I have no idea if it sours or molds. I just made sure when I was done to rinse the spray bottle so it wouldn't clog.