We mix pre-spray by the job, and sometimes different in the same home for different carpet or soiling situations.
The same goes for acid rinse/detergent emulsifier/ acid emulsifier(thanks John).
Different products perform differently over time, but defoaming agents and enzymes loose activity over time according to what I have been taught. I try not to mix more than I intend to use to avoid waste. I DO empty pre spray containers either at night or in the morning prep. before leaving for the 1st job.
My customers pay for the best, so they deserve the best... not yesterdays leftovers. IMHO
Best equipment, Best chemicals, Best systems and procedures, if I can find better, it WILL be on my truck!
31 years and still loving it!
TLC