Yeah, I hate the idea of using LB's as finishers as well. Use the damned thing when it's available and you'll actually save more time in the long run because, ya know, you did more damage with it!

Very rarely is it a good idea to hold back, and even then it's only for specific mechanics on certain fights. So, go wild. Use the LB when it's available, that's why it exists! The sooner you use it, the sooner we can get back to charging it up so we can use it again! If people were less worried about saving it up, I imagine dungeons and raids alike would go by a lot faster.