It is basic human nature to look for security and to hold on to what you have got but if anyone wants to be truly ambitious, then they should be looking to improve their position at least once every 2-3 years – either within their current company or elsewhere.
You should always review your career at six monthly intervals to ensure you are making progress in the right direction. If that is not the case then you need to take action to remedy the situation.
Of course, this is not for everybody, which is totally understandable. People have their own individual circumstances. Dynamic firms are always going to be on the lookout for ambitious and driven people who can help them drive their business forward onto bigger and better things.