Is the C8+ supposed to be a constant light output or should I expect it to continue dimming as the battery fades?
I liked my long lost XinTD C8 V4 XM-L2 T6, which stayed bright until it flashed a couple times warning the battery is getting low.
GeneH
Most stock C8s have 6-8 AMCs with each 350mA regulation
still LED will get dimmer if battery gets below LED voltage plus conduction losses
for real constant brightness you would need a Buck/Boost driver
Looks like some 7135 35M chips stuck on the board. Are those what you are referring to?
Yes, Convoy makes proper usable flashlights, so they have constant current drivers. 
Only the combination of 7135 drivers and XP-L leds is a little unfortunate.
High Vf LED combined with considerable voltage drop over the 7135’s (i think it’s 200mV loss).
You could ask Simon (Convoy store AliExpress) if he can build one with the LD25 driver, which is a 3 Ampere FET CC driver, but only 3 modes and hidden strobe.
You can check here:
https://www.reddit.com/r/flashlight/comments/5l7qhx/zero_reviews_convoy_c8_clear_xpl_hi_18650_993/
Here is the chart:
Good graphs. I wish I would have seen them before I purchased, but not that big of a deal. What I gather from them is at 100% power (like when I riding my bicycle) I’ll get an hour and then rapid fall off instead of a flash that indicates I have just a few mintues before the light cuts out completely like my XinTD C8 V4 did.
Running at 20% for normal use I should get about 2 hours before I start noticing a degradation of light and at 3 hours should be considerably dimmer. I can live with that I think. There’s just something that nags me about changing batteries before it’s too dim to use - that harkens back to running primary batteries dead for the sake of economy.
I have new batteries just arrived today and charged up. I’ll run one down at 20% and monitor the output to see what run times I get until I think it’s too dim.
New Batteries: Panasonic/Sanyo NCR18650GA protected cells arriving from LiOnWholesale
Old Battery: NCR18650 MH 12210
ADDENDUM: I forgot to say “thank you” for the graphs!. sigh