What's the runtime at max output for the Dereelights?
CL1H-T / DBS-T / Night Master
Runtime for the 18650 versions is about 1.2 hrs on high. Runtime for all versions that use 2 x RCR123's (rechargeables) will be about 50 minutes on high, except for the XM-L versions, which run for about 30 minutes. For the versions that can use 2 x CR123's, the runtime on high will be about 1.2 hours.
Using the optional extension tube and 2 x 18650 batteries (DBS-T, CL1H-T, and Night Master), the runtime on high will be about 2.5 hours... except for the XM-L versions and XSearcher, in which case the runtime will be about 1.6 hours.
Using a RCR123, runtime on turbo mode is about 25 minutes. Keep in mind this is a turbo mode, provided to allow for maximum output when needed. Considerabley more runtime is realized on the normal high mode and lower modes.
Does the extension tube for the DBS-T, CL1H-T, and Night Master give you more brightness, more runtime, or both?
The extension tube just gets you more runtime, no change in brightness.
The DBS-T and CL1H-T seem to have about the same lumens rating, I thought the DBS was brighter... why are they listed as the same?
They both have same output (will light up a room the same amount) but the DBS beam is more concentrated (smaller, brighter hotspot, less-bright spill), so the DBS will shine well over twice as far as the CL1H. The CL1H will have a bigger hotspot that is not quite as intense. In trade, it has a brighter spill, and will light up a closer area better.. **Both have the same output as long as the same pill/LED is intalled, and the same batteries are used.
When looking at buying rechargeable Li-Ion batteries, the protected version cost a few dollars more than the unprotected versions, are they worth it?
Yes, it's worth it to get the protected batteries. The battery's protection will protect against short circuit (important), over-voltage, under-voltage, and over-current. A flashlight that has built in protection only protects for under-voltage. On the Dereelights "S" versions (single battery versions) have the under-voltage protection, the others do not.