will unprotected 17670 run a U2 longer than a protected one?

I have a new U2 that will only accept 17670 cells. I have a few protected cells, but I am wondering if UNprotected 17670's will give it anymore runtime? If so, how much more can I expect? Also, is there any protection built into the light? If not, how do I know when to remove the cell?

Thanks for the help.

It really depends on the cell capacity (older cells have lower capacities), although unprotected cells generally have slightly higher capacities. The U2 should drop to lower levels when the batteries are becoming depleted - depending on where the voltage is when this happens, it may be your cue for swaping cells (or a warning that you still have X minutes/hours of runtime left at lower levels). I can't remember what the minimum voltage is to power up the U2 at the lowest level - it may or may not be where it would damage an unprotected cells.

I use protected cells.

The U2 never gets the cell voltage low enough for the circuit to kick in, so I doubt there will be any difference. Using protected cells in the U2 is a waste of money.