My dd was 5 weeks early, however, her body was deeloped as a newborn except her weight (3.2lbs when born) the peds and doctors said she was just a feed and grow baby. She did very well in hospital only 20 days and came home @ 3 .12lbs. she latched on right away and drank enough bm for a 6 lbs baby. Dd is now 3 1/2 months(actual age) and has been on farleys rusks for about a week. Has 1/2 a rusk for breakie, 1/4 for lunch ad 1/2 for dinner plus 5 bottles (4ounces each ) and wakes up in the night for a feed(she never use too) still hungry, takes a full bottle. I tried to increase her milk feeds but she would have nothing to do with it, she actually started to drink less, so I started her on cereal and she is doing great. No constipation problems ,from formula. anymore. she weighs around 9lbs now.
So I think it depends on the circumstances of your premie, health problems advancement etc. and if your premie is ready go for it. I must say though dd is advanced in other stages to so it m ight just be her. She can roll over and wiggle across the living room floor and started to teeth, but slow in the smiling and laughing area took her a lot longer than average. Go withy your instincts and feelings.