I've added three 55 lb bags in my first year. Most salt loss from our pool is through the overflow during heavy rains. The 2nd biggest loss is seven backwashes, accounting for 40 lbs of the salt loss, so that's around 125 lbs going out the overflow. Average annual rainfall here is 48 inches and the past year has been pretty close to the average. I hope that's helpful. Also, you can find out if you have a leak by doing a bucket test:
Get a plastic bucket of pool water and add some rocks to help hold it in place
Set it on the top step going into your pool
Add or remove water to make the water level in the bucket the same as in the pool
Disable your overflow and/or auto-fill
Check it after a day or so and compare the water loss between the pool level and the bucket level
When comparing, a lot of wind across the pool (but not the bucket) or aeration (e.g. spa, water feature, slide) may cause more evaporation in the pool.