At worst the knot will get a bit loose from time to time (like maybe once a year), and then it takes a few seconds to tighten it again.
I expect my shoes will fall apart (they're already pretty old) before this knot unties.
[1] - https://web.archive.org/web/20051203081429/http://web.ukonli...
1. Pick up the laces. 2. Cross the laces over like this... (but don't have them looping into each other like in the picture) 3. and back, leaving loops either side 4. Take the left lace underneath... 5. then back over the top... 6. and wrap round underneath again... 7. and back over the top again. 8. Now similarly with the other lace... 9. underneath, but the other way... 10. then wrapping round as before. 11. Push the lace through the four centre strands. 12. And the same with the other. 13. Then tighten the knot up. 14. Finally, here is an alternate one with an extra turn (at step 10.5).
This is a great shoelace knot as it loosens and cinches tight without untying.