LvB has a travel time - if you cast CL after LvB and are at range there is a good chance that CL will be cast without the CC buff. The preferred "rotation" is LVB-LB-CL to minimise this possibility.


summary

If there is no chance in going OOM then use CL on cooldown
If managing mana is important use CL only with CC buff, use LVB-LB-CL to make sure that CC will be up fo CL
drop CL during BL