How long had Paul suffered before writing 2 Timothy?

Paul had suffered for more than twenty years before writing 2 Timothy. By that time he had endured countless hardships and sufferings, enjoyed few comforts of life, and was deeply grieved as he penned the letter to Timothy. This period of suffering preceded the writing of 2 Timothy.

Les teaches that Paul had now spent 20 some years through all of these hardships and sufferings, probably enjoying very little of the comforts of life. Les explains that it must have grieved and broken the heart of this Apostle to have to come down and by inspiration make this kind of statement, and it boggled his mind as long as he had been teaching the book. Paul wrote this letter to Timothy, one of his young men who had labored with him in the ministry and was now a pastor. He urged Timothy to hold fast the form of sound words heard from Paul in faith and love in Christ Jesus, and to keep the good thing, or deposit, committed to him by the Holy Spirit—that volume of truth referred to as the mystery.

2 Timothy 1:13

Hold fast the form of sound words, which thou hast heard of me, in faith and love which is in Christ Jesus.

Why was it hard for Paul to write 2 Timothy?

Writing 2 Timothy was hard for Paul because it grieved and broke his heart. After more than twenty years of hardships, sufferings, and few comforts, he had to write by inspiration a statement that reflected deep brokenheartedness and was difficult for him to make.