As a quick test, use wire to bypass the tail cap and see if it holds turbo longer. I found the ODF30 tail pad thing did not flex much. When it had soft contact, turbo runtime was greatly reduced. I noticed that turbo lasted much longer when I was measuring amperage at the tail. Bending that metal tab up fixed it.
Here is my ODF30 review with amp draws at different voltages.
Here is a nice video from Mad Max showing how the ODF30 boost driver draws more current as the voltage drops. When the current gets too high the driver steps down to a lower level. So you see how a little extra resistance can lower voltage slightly and this causes the light to draw extra current then step down prematurely. This video shows the basic functioning of all boost drivers. (minus the specific voltages, etc… That of course varies from one boost driver design to another)
The lowest amperage I could get with my ODF30 was 8.35A. Max got 7.6A. This is because of the voltage sag in my battery. I was not at 4.2 volt exactly. It was probably at 3.9 or 4.0 while under load.