The amount of salt you use will depend on your water usage. As noted above, there are generally 2 types...one reads actual usage and one has a programmable time clock. When we had a home daycare, with lots of usage, I'd go through a bag every 2 weeks. Now that the business is no longer in the house, I use a bag every 5-6 weeks. My system has the less sophisticated time clock and I've experimented to where I found that a flush and regeneration once a week is sufficient to keep the water soft enough for me.
Either you're using very little water or your system might need a tune-up. The filter media needs to be replaced occasionally. If the water doesn't feel right, I'd have it serviced for peace of mind.
I started out with nothing & I've still got most of it left
M60 VP160 QS8 EP350