i think that is great advice from pp. i have two friends with prem babes the same age as my ds. one has twin boys who, after the first 14 weeks of their lives, started growing so quickly that at 6 mo they were always hungray and wanting more foods. so she weaned them then. and it was fine.
the other friend has a 7 week prem baby who was still on the small side at 6 months and he wasn't always finishing his milk. some people (incl our equivalent of a health visitor
) told her to wean at 6 months to get him to eat more, which she did, but this resulted in him drinking even less milk and losing weight. she stopped and just continued milk until he really showed signs of being ready, which wasn't until just over 8mo (6.5m corrected)