Over my 50 years in the HVAC industry (OMG … 50 years!) I made it a point to change jobs approximately every seven years to continue to improve my knowledge of the HVAC industry. I never, never ever changed companies to receive an increase in my salary. Salary increase is probably a benefit to job change, although I have known a select few who have switched firms while accepting a reduction in salary so that they could increase their technical knowledge, knowing the financial arrangements would improve over time based on their performance.
With each of my job changes came internal advancements and increased knowledge, e.g., trainee draftsperson to designer, engineer, project manager, and so on, so an employee doesn’t always need to leave a firm to increase their technical skills. With each company I worked for, I was able to enhance my position in the company based on my performance, but at some point decided I needed to move on and challenge myself in a new company and new environment. I’ve gone from consulting engineer to mechanical contracting to construction manager to facility management to troubleshooter and now semi-retired jack-of-all-trades drawing upon all my past experience and past mentors.