I'm assuming by survivors you mean those who attempted ctb and failed. I guess they would probably think the same as other people. I think that in general, if someone ctb on their birthday it is because they wanted to leave on a date that is significant to them or they chose to ctb on that date so those left behind would not have 2 days which would remind them specifically of that person (their birthday and the day they chose to ctb), so therefore someone might choose to ctb on their birthday to try and make it a little bit less painful for those left behind.