i find swing better than mini electric. i have many episodes of blocked ducts with mini electric but none with swing. but pump is a personal item. need to try it yourself.
i also keep a small can of formula milk at home but i rarely used it except when i had mastitis in the first month. i have that to relieve my pressure of milk production psychologically. thank God. we did not touch the can for 3 months already. and there is surplus of breastmilk as well.
i think it is good to keep a small can of formula milk for emergency use. (you can't find formula milk in odd hours when shops are closed.)
first can is similac advance. then, change to snow brand. probably, will change to soya milk for the next can (when the present one expires). cow's milk is not so good mah.
oh. but better than allergy and cancer risk from cow's milk. good that we will only consider that when solid food is introduced, so milk is only supplement anyway.
moreover, when milk is supplementary, the dose needed is relatively low. however, even low dose of allergens in the cow's milk are no good for the babies' immune system at this critical period. that means low dose of cow's milk allergens are worse than the low dose of "hormone" (if any) in the plant product. so, soya milk is not as worse as cow's milk. but the problem is that babies may not like the taste of soya milk.