Initially I thought you could only train one dog at a time- which is technically true. However, when walking two dogs on a single leash that branches into two, they both can hear the noise. After a few days they simultaneously corrected the pulling behavior. In terms of battery life, I only really have them in these collars for a few hrs a day, so they have not run out. Vibration is adjustable, only used a few times because the beeping a verbal cues have so far been enough. Very easy to switch between the two dogs once I got a hang of it. Highly recommend!