If you're using Tommee Tippee Closer to Nature bottles, and have noticed the numbers rubbing off, please ring the helpline, and they will be more than happy to send a replacement out.
I was quite disappointed when the numbers started to rub off my bottles, especially considering that I didn't buy them till after LO was born, and he was mixed fed, so it wasn't like the bottles were in constant use. By the time they were 4 months old, the numbers had started to come off. So I rang the helpline about two weeks ago, spoke to a very polite woman who said they would be happy to replace or refund, and gave me an address to send them off to. I still had the box, but no receipt. So I sent them off with a little note saying how I was disapointed, along with my address, and today (about 11 days later) I have received 4 shiny new bottles to replace the old ones!
These are the only bottles that my LO likes (he will drink from others, but prefers these, plus he doesn't throw up as much or dribble with these ones), so I'm glad I could get a replacement. He's now being bottle fed rather than mixed-fed. I've been using two old bottles for the last 11 days (numbers rubbing off, so had to use a jug and then pour into the bottle, but I needed to keep a couple while the others were in the post).