In one ongoing series of consumer products, my several-hundred-thousand-line codebase lasted for well over 10 years. There was no reason to mess with it. Yes,

In one ongoing series of consumer products, my several-hundred-thousand-line codebase lasted for well over 10 years. There was no reason to mess with it. Yes, I thought parts were messy... but there was also great stuff in it that I'm very happy survived intact. Then decades later, on an entirely different product, in a different business... We had to migrate our product to a new OS platform, as well as needing to fulfill much wider requirements for our customers. The existing code just wouldn't allow this, even if it were stretched and stretched. So I rewrote most of the codebase. In some ways I was tortured knowing we had a functioning product that already handled things I was rewriting (even though it was on an obsolete platform). Especially since the rewriting process takes longer than zero. On the other hand, the new set of code turned out smaller, simpler, more reliable, much more flexible, and is now working well as a foundation our for business. Both sides of the argument make sense to me, I think it just depends on the situation.