I just came across this discussion and find it quite interesting.
First, I would have to say that "saggy" is a somewhat subjective term, so that the "sagginess" of breasts is really in the eye of the beholder. That being said, as I am now in my mid-40s, my C-cup breasts are certainly not as perky as they once were; they definitely have some "sag" to them.
To address the stethoscope issue that has been raised in this discussion, as an adult I have rarely had my heart listened to with the stethoscope on my bare chest; it is almost always placed on the outside of the gown or whatever clothing I am wearing. That being the case, I don't remember a real doctor ever lifting my breast or touching it in any way to move it to listen to my heart. I have only ever experienced this in play exams.
Finally, to the original question about whether doctors tend to examine saggy breasts more or less during a breast exam, I am not sure how to answer this question. In my experience, in general I think my breasts were examined more thoroughly when I was younger because I was told that my breast tissue was quite dense. In more recent years, as my breasts have started to become saggier (and I think therefore also less dense), it seems that breast exams have become quicker, even somewhat cursory at times. Unfortunately, because I have had to switch doctors several times for various reasons, there is the added factor of individual differences between examiners as a confounding variable. Another factor that has influenced the time and thoroughness of a breast exam for me has been the reason for the exam. Whereas a routine exam, especially as I have become older, can be very quick, anytime that I have questions or concerns about something I may have felt during a self-exam has always resulted in a much more in-depth clinical exam of not only the area of concern, but both breasts in their entirety. All that being said, I have been pleased that the last few breast exams I have had actually have been more thorough, leaving me more confident that all feels well there.