Several hours ago, I post a survey request on the list. First, if it disturb some people, please accept my sincere apology.
Second, I'd like to summarize the responses, because I think it might be interesting to some people. I got about 30 responses, which is not a big size. Most people said that they do the planned maintenance during weekday midnight. Two reasons for this. First, it's the time window that will cause the least interference of network usage; Second, it's a better time to get hold of other people (customers, vendors) than weekend if necessary. For some small or critical problems, people just fix it immediately. Some people also mentioned that they would like to major maintenance during weekend.
Third, I will explain our research (routing instability) and hypothesis, which motivate this email survey. Your sharing of insight will be very helpful and appreciated. Because it's pretty long, I put the description in the end.
Finally, we still warmly welcome your survey response. Thanks!