Some say move every 3 years, some think less and prefer contract work. And some think you should feel grateful to have a job and stay in it as long as you can.
I think there will come a point when you either feel you have done all you can in your current role and would like more responsibility. And that's usually a pretty simple thing to rectify. You can ask your manager for additional projects or to sit in on some things you wouldn't normally get involved in and help enrich your role and progress you into other things.
Or you will be able to carry out your role on almost auto pilot. Again this can be ok for you? If it fits around your life, you earn enough to be comfortable and have a great work life balance and no work stress, that is definitely something to appreciate. And consider if this makes you happy. Are you happy with not feeling challenged at work? Beings you spend 80% of your time there! And if you are not challenged at work you have to consider if you do ever decide to move in the future will you have the capability? And will the work world move on and you're left behind. Again there is nothing wrong with being able to do your job with minimal effort if your passions lay outside of work and you just consider it a bill paying exercise
You could decide to move on as you're no longer comfortable with the direction the company is going in. And that's important. You should never feel you are compromising your morals and beliefs for the sake of a job, or that you are being asked to be passionate about decisions you're not comfortable with. If this is the case it's a great time to move on and will give you a great direction of what sort of company you want to work for next. You will be able to make a more informed decision on what kind of career you're looking for and what organisations can support you and your beliefs. Potential employees will also appreciate you are there because they are an organisation you have sought out due to their ways of working.
Ultimately as long as you are happy in your role in every way, challenge wise, work load, relationships, salary and feel you are moving in a direction that will progress you and your skills there is no need to move on within a specific timeframe. People who are ambitious will usually move around more than those who don't feel the need to climb the corporate ladder. However being honest in your current role if you feel you are becoming complacent and would like to take on more could highlight to your managers you are someone they can progress and benefit from progressing in the future. If there is no opportunity for progression then that may aid your decision on whether to look externally.
You have to do what's right for you.
