I dropped squonking back in the reo days because single 18650 just didn't give me the battery life.
What can I expect from a 20700 with a .5 dual Clapton build? I change the batteries in my dual 18650 mod once a day running .4 dual coil at 67 watts.
It will depend on the mAh rating of the 20700 battery. A 3000mAh battery will last longer than a 2500mAh battery, but not as long as a battery rated at 3500mAh.
I use brown LG 18650 batteries in all of my mechanical squonkers, including my Reos. I will use one in my Pulse as well. The Ijoy 20700 batteries are rated the same (3000mAh) as the LG batteries - so the battery life should be nearly exactly the same, assuming the same build. No compelling reason for me to run out and buy new batteries and charger.
If you want to get longer life - buy batteries with a higher mAh rating. But be aware that VERY OFTEN the max discharge rate drops as capacity increases.
And not to be snarky or preachy, but if you didn't understand everything I just posted - you probably should be using regulated mods.