yes, it’s safe. i used it for my kid and he’s a healthy toddler now. for me it’s not how many pumps but rather i wash by the 20th hour after first use. i start using new set at first motn pump and wash at last pump of the day. the residual milk won’t go bad if you store in the fridge. all boils down to personal preference and what works for you. just recommend not to do it longer than 24h
My CL told me about this hack but i read online and seems like it is not safe enough for newborn. Perhaps older baby? I personally dont do the fridge hack
i do use the fridge in the office instead of sanitizing often while working