Those batteries will work great at the power you are using it at. Personally with a good 20watt battery (which the HE2s are, I would keep it below 150 watts or so, and it will be very safe, no matter how low you go on the build. I am being a bit conservative by like to err on the side of safety. At 45 - 60 watts the he2 will not be the longest lasting battery. I would pickup another set of HG2s or Samsung 30Qs to keep charged while you use the other set. It is really nice not to have to wait for a set to charge.
I agree with Jason... Those batteries will be great for the Wattage you're using. I'd not push them (together) above 150W. I personally run a few of my single-18650 MOD's up to 50W with the LG HE2 batteries and have zero issues with them. They are great batteries. Jason's other suggestions for spares (LG HG2 or Samsung 30Q) are spot-on. You should have at least one spare set to charge while another set is in use, and it wouldn't bet a bad idea to pick up six (two sets for spare). Be sure to label them with a sharpie so you know which batteries you have mated together. I use alphabetical... A, B, C, etc. for those used in single mods... A1, A2, B1, B2, etc for dual-mods... this way I can keep track of not only mated sets, but also their position in the MOD, so I can rotate their position each time I change batteries.... 1-2-3, 3-1-2, 2-3-1, and back to start-position, but I"m OCD that way... or as my family tells me... CDO (alphabetical, as it should be, lol).
