If I had swollen lymph nodes for longer than 2 years they must be benign right?

Not always. While it is true that lymph nodes that remain stable in size are "more likely than not" to be cancerous, that is not an absolute rule. In fact, many lymphomas may grow very slowly and not demonstrate any appreciable change in size over a few years. I advise you to seek out medical evaluation, if for no other reason than peace of mind.
Get evaluated. It's not normal for anything to be swollen for more than 2 years, even lymph nodes. Something is causing them to be swollen. Please see your doc to figure out what.
Not Necessarily. I would see your doctor if this is the case. A variety of things can cause swollen lymph nodes and it is important to figure out if this could be something more serious.