Here is more of what your AW IMR 18650 will run like when discharging lower and lower while being used in your PV below =
4.2V – 100%
4.1V – 87%
4.0V – 75%
3.9V – 55%
3.8V – 30%
3.5V – 0%
With that said you wont get 24Hrs out of your 18650 if you an all day vapor more like 8-10 depending I would say on how hard core you are. I'm a bit spoiled and like to have a bunch of batts and once they are below 4v I switch out a Batt if I'm not using one of my VV Mods, and one of the good things about a VV mod is you set it to the voltage you want to vape at and it holds that voltage so you may want to think about one of these. On the other hand using your grand it would also be a good idea to just carry 3-4 Batts with you ( I do ) and this way you always will have an above 4v charge switching them out every couple of hours plus you wont be draining the batts all the way down all the time and they will last longer.
On a second note you also may want to try the Black IC AW 2600mAH 18650 or the 2900mAH Black IC both of these will give you longer run times than your orange 1600mAh IMR AW and they are safe to run, also the Redilast makes a 2900 that is a superb Batt with high quality like the AW which holds an above 4v charge for a long time.