Hi - am about to buy a new mattress for DD1's cot, she is 2.1yrs, but got me thinking, should I be getting a cot bed at the same time, and a bigger mattress, as the mattresses are about half the cost of the overall thing? Planning to keep her in a cot for as long as possible, but she's quite tall... Is a cot bed really that much bigger? Or is there any kind of amazing extending cot bed type thing that would do her through until she is 5 or 6 or whatever? Have had a look online but there are so many different makes am a bit confused! Any help appreciated!