It all depends on baby, why they were prem, their size, whether steroids were given, ect ect. there are so so so many factors.

The following is statistics taken from Lil Aussie Prems, on gestation VS Hospital stay (I've taken out the babies names for privacy reasons) and it is still by far better to reach 36 weeks than what it is any less xxx

23 weeks
Average: 163 days/ 23+3 weeks

24 weeks
Average: 147 days / 21 weeks

25 weeks
Average: 106 days /15+1 weeks

26 weeks
Average: 114 days/16+2weeks

27 weeks
Average: 89 days /12+5 weeks

28 weeks
Average: 74 days/ 10+4 weeks

29 weeks
Average: 60 days / 8+4 weeks

30 weeks
Average: 51 days / 7+2 weeks

31 weeks
Average:41 days / 5+6 weeks

32 weeks
Average: 37 days /5+2 weeks

33 weeks
Average: 23 days / 3+2 weeks

34 weeks
Average: 18 days / 2+4 weeks

35 weeks
Average:15 days/ 2+1weeks

36 weeks
Average: 11 days /1+4 weeks