The most successful projects I’ve seen and been on did rewrite all the code routinely, but one subsystem at a time. This happens when you’re tempted to add a hack, realize it wouldn’t be needed if an entire area were reworked, and mgmt is bright enough to realize that hacks compound in fatal ways over time. The ‘ain’t broke, don’t fix’ philosophy is a good guide here, provided you’ve got a very low threshold for insisting ‘it’s broke’. — Tim Peters, 25 Oct 2000