I have a flock of approximately 1 yr old mixed hens (buff orpington, barred rock, black australorp, etc.) In spring I want to expand. I would like to mark the current hens so I can keep them separate from the new chicks coming in. Once they all get to maturity, I need to be able to tell them apart. Should I use those colored leg bands? What are the drawbacks of using those? Can they stay on for the life of the bird?