The average career span of a corporate pilot is not that long. I'm not going to spout numbers but I recall reading somewhere it was only a couple years. Again I'm talking average time with one company.

Corporate flight departments are volatile and unstable. While this is not universally true the majority of corporate pilots hop around quite a bit between jobs. Mostly jumping around 135 operators to build type ratings and time or looking for that next big opportunity. The job can be unstable and unpredictable. A pilot may say one year he would never leave his job and the next be working somewhere else.