Thats basically it, what are the reasons for getting a new matress for each child?
DD1 is in her cotbed as a bed, DD2 is in crib but growing out of it very fast as she is much larger than DD1 was. So we need to buy a new bed for DD1 and reassemble cot for DD2, but we've just been hit by some major financial difficulties and need car seats etc. so can I use the same matress? Is it really unsafe?