Just that really - I know people who have second/third etc children and use mattress again - I have bought a cot off someone I know, do we need to replace mattress or not? It has been washed and she used it for three kids...its a Stokke cot so the new mattress will be pricey. But I want my dd to be safe too - so I am not being tight, honest - just curious re the reasons/necessity for using a brand new mattress every time.