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You have some slim chance to use them, but mostly only at low to mid levels. This is very emitter type dependent. If there would be D4SV2 with a few lower forward voltage emitter options, it could be even fully useful, but for some emitter types, you will only just get past they being lit up.

I don’t know, what is the power cutoff limit on low voltage, but I guess, it should run until it gets below 2.8-2.9V - which means, you will need to know your battery model, because I have seen IFR (LiFePo4) batteries running near 3.2V most of the time only when current draw is low. When current draw gets higher, they can run anywhere lower in the 2.0-3.1V range, but the voltage will be nearly flat during most of the discharge time. You might want to look up your battery here as well for more info (Battery test-review 26650 comparator).