title_body: What are the conditions for LiPo battery damage from undervoltage?
upvoted_answer: Your questions are challenging to answer because (my opinion) I think there is a lot more that goes into a batteries longevity than voltage staying between a certain threshold.  In addition to keeping the voltage in specified ranges, the following also apply.
  
  
  Do you fly in hot or cold or humid conditions? 
  Do you fly hard and fast all the time where your batteries come off the drone warm or hot, or do you take it easy and just fly for leisure?
  How long do you let your batteries sit below or above storage charge (3.8V/cell)?
  Do you charge your batteries immediately after using them or do you let them sit to cool down a bit (15 minutes or more)?
  What brand of battery do you have?  Some are known to be junk, others have a great track record, but some bad batches now and then.
  What charger do you use?  Is it reputable?
  Do you balance charge?
  How old are the batteries?
  How often have the batteries been crashed?
  
  
  My opinion is, and I've been tracking battery usage since 2011, is that despite the claim of 300+ cycles, most LiPos will only last about 100 cycles due to the factors that I mentioned above, which also includes the occasional oops moments when you fly your battery below 3V/cell or on the rare occasion when you forget to put them in storage charge.  On top of that, the number of cycles is highly dependent on the quality of the LiPo.  
  
  To make a long story short, a few mistakes with your batteries every now and then might "damage" them, but it shouldn't affect them as much as other factors involved in flying, like crashing and the others that I've listed above.  Generally speaking, if you take care of your batteries, they should last you a while.
  
  I know it's a vague answer that doesn't really hit on your voltage questions, but it's based on many years of experience, so I hope it helps you out.