Can't comment on the 510s, but I recently got a Vapor King from V4L (Kr808D-1 manual) and am really satisfied with it.
I vape about 3mL/day atm. Each battery fully charged seems to last around 3-4hr, or about 1-1.5 cartos. Charging is pretty quick as well (about 3hr to charge the battery from dead to full), so I've been just swapping batteries back and forth, one vaping and one charging.
Hope that helps with any 808 info ya needed =)
I vape about 3mL/day atm. Each battery fully charged seems to last around 3-4hr, or about 1-1.5 cartos. Charging is pretty quick as well (about 3hr to charge the battery from dead to full), so I've been just swapping batteries back and forth, one vaping and one charging.
Hope that helps with any 808 info ya needed =)