Last night was the first night of selichos and in Israel חצות was about 12:30 so many shuls started selichos at 12:30. Many shuls have a minhag where the Rav talks for a few minutes before selichos to inspire the people. This is a very fine minhag, however, the Rav should realize that it is very late and that people want to start selichos on time and go home and go to sleep. Sunday in Israel is a regular workday and people cannot sleep late. For the Rav to plan to speak for 15 minutes and then speak for an extra 10 minutes is really not right. To start selichos 10 minutes late at such a late hour is a tremendous טרחא דציבורא.
There is a famous saying that to speak for 10 minutes is much harder then to speak for an hour. When you have a short time you need to really hone your message and measure your words. When you have an hour you have much more leeway. Unfortunately, there are some people who can never fit what they want to say in the allotted time. If you give them ten minutes they speak for 20-25. If you give them an hour they will have enough material for an hour and a half.
This really bothers me. Many times it points to a lack of discipline and preparation. I speak publicly every so often, and when I do so, I go over exactly what I am going to say a number of times before I actually speak and time myself. If I have 10 minutes to speak then I will make sure that I have enough to say for 10 minutes and not more. The same goes for 40 minutes or an hour. I don't understand how you can prepare a speech that is allotted 15 minutes and take 25 minutes. That is almost double the time.
Last but not least, I think it is counterproductive for a Rav to speak for 30-40 minutes on Shabbos morning. It is simply too long. Most people on Shabbos morning are tired and simply cannot concentrate for that long. After 10 minutes people simply lose it. There is no reason why the Rav cannot say over idea that he is saying in 30 minutes in 10. It means that he will have to work very hard to refine and hone his message and cut out a lot of extraneous stuff. However, in the end people will be much more attentive and may actually get the message he is trying to convey as opposed to listening for 10-15 minutes without hearing the main message and then tuning out.