This can help a lot when determining what is a fake description of the performance. Generally don’t trust any listed lumens unless someone has measured it or it’s from a company known for accurate measurements of flashlight specifications.
If you want 2 hours at 500-1000 lumens you’ll need a 3400 mAh cell and a 1400mA driver and you’ll have to suffice with the lower end of your lumen desire (around 500).