The CIC manual called OP 6 has the following to say on language test validity
Language test results must not be older than one year at the time of application.
Note: Points for the applicant’s language proficiency are generally awarded according to evidence provided at the time the application is made. However, if further study, training, or testing is completed and documentation submitted between the time of application and the time of assessment, officers will use the most current results to determine point allocations. In terms of designated language test results, officers will NOT select the highest score for each language ability from a variety of test score submissions. It is always the most recent group of tests that will be considered by officer as it is the most current assessment of the applicant’s four language abilities.