And yes, you're right, his cartridges probably would have run out at some point. With that said I'm sure he also had to use the bathroom at some point too and we never saw that either did we? Also his webshooters were destroyed twice, meaning he had to take them off to make repairs.
Just because you didn't see it doesn't mean it never happened.
Also I was under the impression they created the biocables solely for the purpose of selling them. Is this not a multi-million dollar business? They need to make a profit on something don't they?