Well, I am one of those guys. 3 planes with those, one flown every week in the summer for 5-10 flights each time. About 4 years. But point taken.
These batteries are what I put in my bigger planes:
https://electrodynam.com/rc/EDNano/index.shtml, but their smallest size is 2500 mah, which in an LT-40 will get you well over 13 hours of flying before you need to recharge. And they cost $52.
These are a more reasonable size, and cheaper:
https://www.chiefaircraft.com/spk-b900lfrx.html Haven't used, but if Spektrum puts their name on them, they should be a little trustworthy, one would hope.