Topic: Number of images in one Auto Viewer gallery

I would like to get peoples opinions, purely from a "good web design" point of view, about the maximum number of images in one AV gallery.  I am about to add over 150 images to my AV website and am concerned about how many images will visitors watch in one slideshow. Currently, my largest gallery has 27 images--

I now have 3 new portfolios to add that have over 50 images each. What do you think? Should I put each new portfolio in one large 50 image gallery or break them into sub galleries? I realize people can click the next arrow at anytime, but 50 images would take several minutes to play through. Is this too much to expect for the average visitor?