I got this habit of frequently updating of my resume from my consulting days, and I think it is a good habit. I used to update it every month back then, but now it serves to do so every half yearly or so.
For one, you do not need to crack your brain trying to remember what you have done and achieved over the years, especially when you really need to produce a resume in the nick of time.
It is also a good way to review your life and your career, and think about what you would need to do more, or not do anymore and what else you would like to be doing.
And what more with platforms like LinkedIn, you can also network with others and request for recommendations and get endorsement of skills.