When is it time to change the hoses ? If it ain't broke don't fix it. My hoses are 93, no smell, I always flush a few times with clear water before we button up the boat to come home. Same after my morning constitution. Duck bills, seals, switches all work like new, occasionally have to prime the rubber seal in the bowl with some silicone and a rubber glove, but only in the spring during summerizing.. Vacuflush rocks !