Hi Dennis,
1st, as I said before: I'm with Alan and Dean, I just fly them out of the box. I'm glad that Dean clarified for us how relatively easy we are on our batteries. I know that on our 5S and 10S RC batteries we push them hard on the long up lines and need every bit of their 25C/50C ability for the several seconds of doing vertical snap rolls etc. But, as Dean said, we don't push our ECL batteries very hard. Our up lines are relatively short (90' vs >500') and get some of their energy from the "zoom" of the level flight speed. I don't think we need a break in period. BTW: I do take it easy on the 1st few flights of my new ERC batteries, but not the ECL ones.
BUT: Mike has a good point about discharging our new batteries as a "smoke (balloon?;-) test" before they get a chance to bring your new plane down in flames! I don't think this is needed for the top two name brands, Thunder Power, and EVO (FlightPower), but it may be a very good idea for the "no-name" brand packs.
I just counted my batteries and I have 33 Lipo batteries, from 3S 1200 mAh to 10S 5000 mAh. Most of them are Thunder Power (high quality batteries, assembled in the good ole USA, in LV NV :-) with several FlightPower packs. Over the past 6 years of flying with LiPos I have never had a failure of a Lipo from these two brands, except for four I injured myself (please don't ask ;-).
I strayed only once, a friend talked me into trying one of those red China packs that were 1/2 the price. It looked OK when I received it. It took me a few weeks before I pulled it out of the box again, to solder on a deans connector. It had already "ballooned" before I could even get a deans on it. I put it in a saltwater bath for two weeks and sent it to the landfill. Obviously I am not saying they are all bad, my friend uses them with only a few mishaps, but I don't like to worry about my power system and I think that it is worth a few $ more to have peace of mind.
Of course, your milage may vary.
Regards,