E-cigarettes have been gaining in popularity, so that means there are lots of new manufacturers, which makes the decision process quite difficult. Can you help us out with any features you are looking for, and maybe a price range? When you say "long lasting", do you mean battery life or total lifetime/durability?
Generally the "Joye" ego products are pretty widely recommended for a decent starting point. There is a "twist" version, which allows you to dial the voltage like many of the more expensive
mods for less than $30 per battery. I have been using these along with a kanger t2 clearomizer with great success for around 2 weeks now.