Oh, padawan, much changed the vape scene is!
510s and cartos are still with us. If you loved it and have a backlog of equipment that would otherwise be landfill, then by all means, stock up and go.
But over the past couple years, you have missed some big improvements. If cigalikes are your thing, check out the Joye eRoll. It's an automatic that has shorter battery life than your 510s, but comes bundled with a fast-charging (and classy looking) portable case that makes it easy to swap-and-charge two batteries all day long. The eRoll delivers higher, more consistent voltage than the 510, so you get much better hits. And it comes with a very easy-to-fill tank system that uses no filler material. Proprietary connections, though, so not compatible with any of your 510 gear.
Ready to move up in battery size? The eGo pen-size battery now comes in variable voltage models -- including the Twist, the Spinner, the Winder, and several others. VV lets you tune in the best voltage for your delivery device and juice flavor. Pair that feature with the newer generation clearomizers, like the Viva Nova for warm top coil, the Protank/Evod/MT3 for cooler bottom coil, and you'll have a whole new experience with taste and vapor production.
I started with the 510 early this year. Picked up (and test drove) the eRoll for a friend recently and, have to say, I was seriously impressed with that little beauty. But for myself, I'm now rocking a Vamo with Kanger Protanks and using Spinners as back-up.
Start your browsing, as you have much to catch up on. And welcome back to vaping.