For what it's worth I've carried a Surefire E1e-HA with KL4 head every day for, what has to be, at least five years now. I've even carried it in the same pocket as my keys the majority of the time. Believe it or not, it still looks near brand new, with the coating just slightly worn around the edges and on the rubber button. The glass isn't scratched/chipped up either, thanks to Surefire's sapphire coating.
I've taken this thing everywhere. I've had it snowmobiling where it was -30*F, I've had it in Aruba, the Bahamas, I've used it working construction, I've swam with it in my pocket, its been buried in sand and clay, it's fallen from a scissor-lift onto a concrete floor. Even through all that I've never had a single problem with it. The only maintenance I do is clean and re-grease the threads every six months or so.
IMO the KL4 head is worth it. I've never seen a more durable flashlight. I used to kill Maglights all the time, I rarely had them last more than a year. Yet I don't doubt this Surefire will last me for at least another 5 years.
On a side note the KL4 head is 100 lumens now, not 65. Even my older one on my single battery E1e body is very bright, enough to temporarily blind someone (as I've found out on a few occasions.) It's nearly as bright as my regular E2e.
Now, on the E2e body the KL4 has more flood than the regular E2e (making it good for searching inside a dark area), but I don't think it throws as much light over a distance as the regular incandescent E2e does. It's pretty close though. Either way, I've never felt lacking with the KL4 driven on one battery, never mind two.
You can see my light in this picture: