Our philosophy is that you should never hit our storage limits if you're not abusing the system, so while we do have soft caps on storage, you're unlikely to ever reach them.
We look at storage by "Storage Units." One card is one storage unit, and one upload is ten storage units. We have a soft limit of 3,000 storage units created per user per month. If you hit up against that limit we'll reach out to you to see how you're using the software.