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...
Super easy to untie, as well, if needed.
Also on my Solovair boots, I used quick tight lacing [0], which gives you the outer "straight lacing" appearance but also allows you to make the boots very tight without spending 5 minutes to tie them. The main issue with this technique is that the laces can shift, but I marked the center of the laces with a Sharpie to serve as a guide.