I am very anal about my batteries and always do formation charges (for Nimh) or Cycling of packs and record the readings on my battery log. I believe It is important to establish a base line of a packs capacity and internal resistance so that you can monitor the health of your batteries and spot a problem before you risk losing your model. I also check my voltage before each flight. Additionally I pay attention to how much charge each battery takes and this allows me to understand how many Mah I am using per flight. If you are this intimate with your batteries, you should spot trouble a long way out. Proper storage is important also so based on your batteries chemistry there will be different requirements. To help me understand my batteries Internal resistance (IR) I purchased one of these units shown below. Here is a link to a thread that tells all about what this unit is and what it does. This read was over my head for the most part but I did get help from the experts to understand enough about how to use this for my intended purpose.
https://www.rcgroups.com/forums/show....php?t=1323465