Energizer lithium AA question

So awhile back I did a run test with some L91's. They start out at 1.7 volts. At end of test they were at 1.5 so still plenty left. When I went to use one I only got about 15 minutes of runtime in a light that normally should go for 2-2 1/2 hours. Now the run test I did with them initially was with a Malkoff Dropin and they were in use for like 50 hours. I was figuring that at 1.5 volts they were still basically 80 percent full but think I'm missing something. Did the long drain time just kick there butt or is 1.5 for these cells almost dead? I have used this type of cell for years and didn't think 1.5 was on the low side. I have a decent tester that measures the cells under load so I know that's not it.

Energizer lithiums are mostly depleted when they get to about 1.6v open circuit voltage.

Ok well that would make sense then. But boy, I have done test with them and have seen them go all the way down to .600 or so.But they did have a lot of use already on them.

Their curve is way different than alkaline AA.

HKJ's low-drain graph indicates it dies at about 1.4v. Maybe there's some slight rebound to a higher voltage at full rest, but yeah, only 15 minutes left at 1.5v sounds reasonable.