The main issues people have with help file performance
(regardless of whether it is a CHM file) are related to the number
of images, DHTML hotspots, bookmarks and links they have in a
topic. The number of topics in a CHM should not be an issue. What
exactly are you trying to access the performance impact of?
The main issues are listed above. The number of topics in a
CHM does not really cause performance problems. More logistical
maintenance problems which is why some use several CHMs merged into
one. As far as size/performance of an CHM file is concerned, most
are relatively small.