What is "frequently"? I'd like to see a minimum of three years ahead of a transition, and a decent story why. Often the contract ends, the company is sold and the new policies are draconian, etc. Fine.
Given the level of effort involved in bringing someone on, my outfit cannot afford to be staffed like a fast food joint.
From memory: last I heard the average is 18 months. I don’t know if that was accurate then or still is, nor how much it varies regionally or by any other criteria (I can look it up later but had a quick moment to reply and HN moves fast and might fill in the gap before I can take more time to look).
Consulting is a little unique in my experience - if there's a steady stream of work, you never really stick with the same client full time for the full 5 years. It's a lot easier to keep your skills fresh and move around to find interesting challenges
Does your employer offer its people the 10-20% annual salary increase so they do not have to look elsewhere for what the market is willing to provide? I ask this seriously.
Given the level of effort involved in bringing someone on, my outfit cannot afford to be staffed like a fast food joint.