"It is the rare person who has a single employer for a whole career, and employers understand this. So it follows that it is unreasonable to expect employees to accept becoming useless to other potential employers, however invaluable they may have become to their current employer.If your skills and knowledge are valuable only to your current employer, you are in trouble.Sooner or later, for one reason or another, your employer will no longer be interested in buying those skills, and you will have no place else to sell them.Obsolescence is bad business for employers as well as employees.It is costly for employers to disposition the obsolete, and to hire or develop employees with the skills that the departed should have been developing all along.”W. J. KING & JAMES G. SKAKOON, The Unwritten Laws of Business (2007)The bestselling classic The Unwritten Laws of Business was first written more than six decades ago, and updated more recently for a modern audience. What is amazing is how timeless its lessons are, and how relevant they are for what we consider to be our technology-driven age.One of the many principles it highlights is this: "Maintain your employability as well as that of your staff.” Consider that this thought comes from a bygone era when lifetime employment in one organisation was not uncommon.Even then, some enlightened fellow had the insight to view things differently. The thought is expanded in the excerpt shown to the left.What was a telling point way back then hammers itself home today. In today’s fast-changing world, who among us can afford to say, "That’s it, I’m trained; I know what I need to know for the rest of my career.”? Try that even for a year, and see where it gets you.But there’s a problem. Employee (and especially senior employee) churn has never been higher. People don’t stick around in companies like they used to. They move on, quickly and frequently. So why should any one company train them? CEOs and human resource heads often tell me: "It’s a mug’s game, training. You pay for people’s development only to find them moving on and using it to good effect elsewhere.”I trust you’re not one of those leaders.Today, skill-sets need continual upgrading. If you’re still sitting in the same place doing exactly the same things in the same way that you were doing five years ago, I have bad news for you. The day is not far when your company comes to tell you it no longer needs you. You will be replaced by a smarter employee, or even a device. So don’t accept zero personal development.It is equally silly for employers to stifle skills development. Your business of five years ago may resemble your business today, but here’s a safe prediction: your business five years on will look nothing like today’s. You can hold me to that little prophecy. Suppressing personal development in your key people will have only one result: obsolescence.You will go through all the pain and cost of redundancy, and end up looking for expensive new people. It is, thus, far better to keep investing in people today and tomorrow, and keep a healthy budget for employee development.Accept fully that you’ll lose a proportion of your people, and recognise also that you’ll receive a bunch of people trained by others. That’s the way it goes.A final word for employees with any ambition: don’t sit around waiting for your employer to find the money to spend on your training. Invest in yourself. It’s your life and your career, after all. In today’s world, with all its opportunities for self advancement, you have no excuse.Find the money, find the time. Take charge of your own development. It’s no one’s problem except your own.