Having been in this situation, as well, I find that the aging out of technology MUST be led by a CTO who is competent enough to know that tipping point of cost-

Having been in this situation, as well, I find that the aging out of technology MUST be led by a CTO who is competent enough to know that tipping point of cost-benefit. Their job immediately becomes a political choice (pass the pain to the next guy) when the point has passed and it gets worse every new CTO. Some of these systems are HUGE (hudreds of millions of lines of ColdFusion, where I worked).