We used them for a few months due to pain (as it turned out DD had a tongue tie - snipped at 3 weeks but took a while for attachment to get right), didn't have any problems with supply or weight gain, just stopped using them after a while (think I used them for some feeds instead of stopping cold turkey). We used medela ones provided by the LC and they were fine, although bought a different brand when I went away and forgot them. All in all I just trusted that things would work out and they did, didn't stress too much about supply just kept on feeding. Good luck, keep at it