Could be. What part of the country are you in? Is the pool ran all year around? The salt generally doesn't get out of the pool. The only loss of salt you will have is from backwashing (with a sand filter), vacuuming to waste, and splashing. Even when the water evaporates, the salt remains in the pool. It does seem odd that no salt has been added over such a long time, though. Is is possible he is adding and you don't notice? You shouldn't need tablets other than in the winter when it's too cold for the salt system to generate. Actually though, salt is a lot cheaper than tablets, so it really doesn't make sense that he would be using tablets instead of salt, especially if he is not charging you separately for the chemicals he uses in the pool.

What salt system do you have and is it calling for salt now?

You need to get your pool water tested to see how much salt (ppm) shows up. It is unlikely you are receiving the full benefits of a salt water pool if no salt has been added in all that time.