we put 1st dd into a bed at 19mths cause ds was on the way, i didn't use rails we just had a mattress and base set (took the wheels off) so it was flat and low on the floor, put the cot mattress beside it and voila - all good. however we waited until ds was 3.5yrs old when he was moved into a bed and get this he still called out in the morning that he was awake and could i get him pmsl - he didn't realise he could get out for another few months - personally i think if they are not attempting to climb out then if you can leave for as long as possible, i know with lani she will stay in until she is at least 3yrs old cause she is also tiny, and even if we have another there are so many cots i can borrow from my circle of friends.

good luck