> With the code that I spent the most time designing (assuming I eventually came up with a good design), the more the requirements change

Your use of "assuming" is interesting. Sometimes it's hard to know if it really was a "good design" until after the requirements change...

"The competent programmer is fully aware of the limited size of his own skull. He therefore approaches his task with full humility, and avoids clever tricks like the plague." - Dijkstra