3 years is no time. I have userland code that still works 15 years on. The problem is only if I want to change from jQuery 1.x or some ancient CSS library... it would break completely. I can live with that. What I can't really live with is the 500,000 loc I wrote in Actionscript 3 being permanent unusable and unable to run anywhere, ever again. That kind of thing makes you never want to work on another project.