Why do some application processing times change and others do not?
This is normal because the volume of applications may vary from one month to the next. Rest assured that files are still being processed.
In many cases, a file is waiting in a queue for initial review. Applications are processed in the order in which they arrive. Some take longer to process than others. There is no maximum time frame for reviewing an application.
this is from - http://www.cic.gc.ca/english/helpcentre/answer.asp?q=032&t=3