Loofah Replacement?

Last time I purchased a new loofah 
(Plastic netting bath sponge thing) the tag recommended that it should be replaced every 30 days. I try to replace mine fairly often but I definitely don't do it every 30 days plus sometimes I use a washcloth instead. 
So just wanted to know am I the only one not doing it every 30 days?
Do you think it's wasteful to replace it that often?

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