I have a 510, and I just got some PTB's last night. I used the Double Fold, Rolled, Frayed PTB mod, aka the "rho" mod.
I was dripping or topping off every 7 or so drags, but after using the rho mod. I went three hours without having to touch a bottle of juice, and then it was just a drop or two to help the capillary action. This was at home, where I vape near constantly. I grabbed a couple of my other carts, modded and filled them, and stuck them in my PCC. I'm taking these to work tonight to see if I need to top off at all. I don't think I will.
-Rook
Edit: I'm using the same thing Niniane linked you to. I would suggest reading the whole thread for the final evolution of the mod.