IELTS score must be valid in the date you submit your documents post ITA (AOR date). I mean, the date you took the exam must be 2 years or less from the AOR date.
Even if it is valid at the ITA date, if you submit your documents later (and the test date becomes more than 2 years old), then you would have to present new IELTS score that is updated. I think if the score doesn't go below the minimun CRS for that draw with your new IELTS scores, then you'll be good. But if new IELTS score makes your score go below, then you'll have to decline the invitation and enter the pool again with your new score.