With regards to IELTS test results for skilled worker applicants, the rule is that they must not be more than one year old at time of application.
For example if you applied for immigration on 01 July 2009, your IELTS result should not be more than one year old on the above date of application and it shall continue to be valid till your immigration process is completed/finalised, irrespective of the time/years taken by CIC to take final decision on your case. In the old processing pre-26 feb 2008 cases, it took 5-6yrs to take a final decision. The IELTS result remained valid till a final decision was taken, so in this case valid for 6-7yrs, if it had been take within one year of application.
Hope this helps.