I have a CL30R also. Mine came with 3 2600mAh batteries. 2600mAh's in a low drain battery is pretty lame by today's standards, so if you go with a 3400 or 3500mAh set of course the run time will improve quite a bit. The lantern does have low voltage protection, it shuts down at about 2.8V. It's still possible to damage an unprotected battery. The scenario would be if you let the batteries drain down to a point where the lantern shuts off, then leave it unattended for a few weeks or more in that condition. The parasitic drain combined with the self discharge could bring the voltage below 2.5V, repeat that process a few times and you have damaged batteries. My experience with LG MJ1's from Lion wholesale has been very positive, because they are higher capacity and higher drain than the originals you will see big improvements in run time especially at the highest output.
Frank