Three years. LOL In my defense, I've come home to be a stay at home mom and I'm only 27. Technically I left to go to college and then came back but my employer let me keep my years of service when I came back and reinstated me in my position when I came back. I babysat for his son for years before I worked in his office.
Interestingly, it is where I met my DH.. even if we weren't married while we were there. We started dating when I when I returned to the company although he didn't work there anymore.
DH has been with the same company for 4 years this July. But his company is up for being bought out. It's actually the same company that bought out his old company and then laid him off. Soooooooooo.. we don't know what will happen or if he'll be able to combine his years of service.