I always include some extras just in case as well.
Only had one complaint. She said none of the seeds germinated. I offered to send more. No response. I had also started some of the same cross (from the same package before repackaging to mail) and mine germinated. I offered to send her little germinated seedlings. She still put in a complaint. I was mystified as I thought I had offered several options. I ended up refunded the money. It was her loss...she could have had seeds already germinated (as little plantlets). Just can't please some people.
Interesting to hear of other stories. I wonder if radiation/heat/cold in the mail does anything.
Mostly have heard of good things and pics of pretty flowers!