How fast a CD can be read depends on the read speed of your drive ie 52read 16 write 8 rewrite quoted in the manufatures manual
A whole CD should be readable in a few minutes.
What slow things up is when the quality of the disc is poor and the software is constantly searching for the contents of a file. CD-RW discs are renown for rapid detioration and should not be used for storing valuable data over long periods ie months. you did right in archiving to several different brands but wrong in using CD-RW use CD-R as discs are now very cheap 50p each.