How many companies will be around in 30 years? Half the companies I've worked for in the past do not exist anymore. The idea that you could get a job and stay

How many companies will be around in 30 years? Half the companies I've worked for in the past do not exist anymore. The idea that you could get a job and stay there until retirement is antiquated at best. Guessing that I'm less than 10 years younger than you, I had a college professor that told my class to change jobs every 5 years to maximize income. That was in the early 90s.