<p>I wouldn’t use Tulane’s biology department as a prototypical example of typical engineering PhD programs. For one, it isn’t engineering.</p>
<p>Most doctoral programs in engineering that I know of have something more like this: a 7-year deadline to finish before being penalized (e.g. by having to pay full, OOS tuition) and a 10-year harder limit before credits start expiring. For the most part, these penalties are more of a penalty on your advisor for not getting you through the system faster since they are often ultimately the ones having to pay for your tuition.</p>