Sebo and the shedding dogs

I am contemplating getting a sebo for ny next vacuum after having a Dyson. I am not against bags in general, but I'm worried I'd just end up paying a fortune in bags. I have two heeler/australian sheps. They amount they shed between them would spawn another dog with hair alone. So my question here is if anyone has similar situations, how long does the bags last? I know it's supposed to pack in there pretty tight.