Well they say that their suckling reflex doesn't kick in until 36 weeks, which is when we tried with Lola but that was incidental as she was born at 35 weeks so it was only a week later.
There was a 31 weeker in SCBU with us who was happily suckling away on her Mama though. I think it totally depends on the baby. The littlest ones tend to burn off more calories than they consume trying to feed orally, so at our SCBU they let them oral feed for a while then topped them up with a tube feed.
If you want to try Elias on a feed and see how he does it can't do any harm. The sooner the better really I say since they tend to leave sorting out oral feeding to the last minute in neonatal units and then establishing feeding can take quite a while and is the only thing stopping you from going home which can be quite frustrating!! Also if you have trouble, try the Medela mipple shields, they have been a lifesaver for us.
xxx