Tommee Tippee Closer to Nature Baby Bott

I've used Tommee Tippee bottles and nipples for both of my little ones, and I love them. My babies have never seemed to have issues with gas, although I can't say for sure that that's because of these bottles/nipples. I've always used the slow flow nipples for the entire time until they were done with bottles. They always sucked down a bottle quickly enough, in which I didn't like the idea of getting faster flow ones so they could down the milk even quicker. They wash and wear well. With my first child, all of the nipples were still in good enough shape to reuse for my next child if I had decided to do that. (But I did buy new for my next one; mainly just to appease my conscious.) I always hand washed them though. I was afraid of them getting too worn if I were to use the dishwasher, but I don't know that.