I left my first job after two years because I felt I was not going anywhere and there was nothing to learn. I was given all the simple task to do. For every project, the project leader would have meeting with the senior staffs and figure out what kind of tasks. They excluded me in every meeting. I was just given the task written on a piece of paper.
The average number of years I stayed in a job was two years. One job I stayed for five years, I loved the job and I thought that would stay there. Unfortunately they changed the vice president, after six months, 10% of the staffs were resigned (including me), one guy worked there for 19 years resigned, it told you how bad it was.
Another job I stayed for 8 months. It was one of a division of a fortunate 500 company. They told me the division was solid. After six months, the company announced to sell off that division, if no one bought it, they would close it down. I immediately found another job.
Things changed so fast these days. Even you want to stay in a company, maybe the company does not want you. The other company I worked for decided to outsource the IT department to India.
If you are still young and only work for IT for two years, I would think about switching career !!!