Brant Pitre and Richard Fellows are having an excellent discussion on dating the pastoral epistles. Check it out here. My jury is still out on this issue, especially since I've heard Luke could have composed these letters. Which makes things a whole lot more interesting... S. G. Wilson notes the following parallels: 1. Paul looks back on his past career with some confidence, believing that he has fulfilled the tasks designated for him (Acts 20:18-21, 25-6; 2 Tim 4:6f.). Moreover, the striking metaphor of an athlete finishing his race is used in both Acts 20:24… and 2 Tim 4:7… At the same time he is deeply concerned with the fate of the church in his absence. This is indicated by the whole of Acts 20:17-35 and each of the Pastoral Epistles. 2. The problem Paul foresees and warns of is heresy, which will assault the Church from within and without (Acts 20:29-30; 1 Tim 1:3f. 3:1f; 6:20f; 2 Tim 2:14f. ; 3:1f.). The heresy appears to be an early form of Gnosticism and its centre is in Ephesus (Acts 20:17f.; 1 Tim 1:3). Paul urges constant alertness (Acts 20:31; 2 Tim 4:2f.). 3. The responsibility for resisting the false teaching is placed on the church leaders or on Paul’s assistants. The church leaders are, in both cases, elder-bishops (Acts 20:17-28; 1 Tim 5:17; 2 Tim 2:2; Tit. 1:5f.), and it is Paul’s example and instruction which will be their chief weapon (Acts 20:27, 30-5; 1 Tim 3:14; 4:11f.; 6:20; 2 Tim 1:8f., 13-14; 3:10f.; Tit. 1:5). 4. Paul speaks of his own suffering for the sake of the gospel (Acts 20:19-24; 2 Tim 1:11-12; 2:3; 3:11) and indicates that for him a martyr’s death lies ahead (Acts 20:25, 37; 2 Tim 4:6f.). 5. The ministers whom Paul appoints and exhorts are warned of the dangers of the love of money (Acts 20:33-5; 1 Tim 6:9-10; Tit. 1:11). 6. Paul commits his successors to the Lord and his grace (Acts 20:32; 2 Tim 4:22).  S. G. Wilson, Luke and the Pastoral Epistles (London, 1979) pg. 117f.