ANSWER: The defence is not valid, because the time for any state status of limitations for contract action starts when all facts about the breach has been found, and it has been concluded that a breach of contract actually happened. The time does not start when the breach happened, but when facts has been generated to show that a breach actually happened.
The plaintiff actually have more 5 days to file his case because the fact about the breach was known on the 20th of January, 1986 and his case is filed in the court on 15th of January 1990.
Therefore the plaintiff case is valid, and should be processed by the court, while the defendant defence is invalid and should be ignored by the court.