I bought 1.5m and it lasted until she was about 8 months (we stopped after that) but it left enough that I could tuck the ends in so it stayed secure.

I just folded the raw edge and ironed it, then folded and ironed again so there's no frayed bits visible, then sewed a straight line. Couldn't be easier, plus there's some cool patterns out there that you can't get with the bought ones!