Contingency Fees V. Billable Hours

While a colleague of mine was on vacation on a cruise, he met two lawyers: a patent lawyer who bills by the hour; and a lawyer who bills for his services on a contingency fee basis.  It was striking to my colleage to notice the difference in attitude and lifestyle between the two lawyers.  The lawyer who billed by the hour was constantly working and exhibited stress during his vacation; he also seemed incapable of truly escaping his work.  The contingency fee lawyer, on the other hand, seemed dramatically more relaxed and didn't do any work during the cruise.  The projected attituded of the contingency fee lawyer was that his work would wait for him, and that he could pick up where he had left off after returning from the cruise.  Are billable hours less conducive to a healthy lifestyle?