For me, I run 3 different compounds and do daily injections, so by drawing 7mL of oil from 3 different vials into a 10mL syringe and then into a sterile vial. Then I draw 7 times from the mixed vial. Total entries into. Vial this way is 10 per week as opposed to 21 per week when entering each vial every day.
Looking at it this way I feel like the way I am doing it is actually less prone to causing an infection or introducing bacteria/other debris into the vials. But that is purely conjecture and I do see your point as well.