breastfeeding mommas...

Have any b-feeding moms introduced the bottle at all? My husband gives 1 bottle a night with breast milk and 1/2 formula so I'm able to sleep a 4 hour stretch.. baby is 4 weeks and that's the longest stretch I can get.. I know you're not supposed to go long without pumping or feeding due to maintaining supply. What is everyone else doing ? What about a bottle during the day if we're out running errands or go out to dinner?