How to meet demands of employers?

Some jobs I have had in this country is okay but problems come after the 3yr period. I find employers appreciate the work done, but after they give a few raises, they expect too much in return. After 3 years they get too demanding and treat you like you are a lazy worker, yet you are a good worker and do the job everyday and meet the requirements. They also can nit-pick over the littlest things that are meaningless.

Is pushing you more and more a normal procedure, or management technique? The company is not going out of business, and as a matter of fact they make more profits year after year.

So what do they really want? They want you to quit and hire someone else for cheap?