Many have wanted to hear my take on this, here it is. The truth is that the verse that many have stuck their heads into, debunking ETERNAL SALVATION is a result of lack of proper understanding. To begin, I'll be comparing two verses (note the uppercase): 

2 Timothy 4:10 "for Demas has forsaken me, having loved THIS present WORLD, and has departed for Thessalonica—Crescens for Galatia, Titus for Dalmatia." ( NKJV) 

1 John 2:15-16 Do not love the world or the things in THE WORLD. If anyone loves the world, the love of the Father is not in him. For all that is in the world—the lust of the flesh, the lust of the eyes, and the pride of life—is not of the Father but is of the world. 

Comparing "this world" and "the world", which are "aion" and "kosmos" respectively from the Greek translation. — "aion" means "this era", "period", "time", while — "kosmos" means "earth and it's inhabitants". 1 John 2 uses "the world" — "kosmos" and all that is within it [inhabitants], which are the lusts — of the flesh, the eyes and the pride of life, in a nutshell, SIN. But in the case of DEMAS, it was not so. Rather Demas loved "this present world", as in, he loved "this present time", he wanted to live, he didn't want to die. Obviously, Paul was taking some risks in which an ordinary man would not want to take. 

Acts 21:4-13 (concised) 

[4] And finding disciples, we stayed there seven days. They told Paul through the Spirit not to go up to Jerusalem. 

[8] On the next day we who were Paul’s COMPANIONS departed and came to Caesarea, and entered the house of Philip the evangelist, who was one of the seven, and stayed with him. 

[11] When he had come to us, he took Paul’s belt, bound his own hands and feet, and said, “Thus says the Holy Spirit, ‘So shall the Jews at Jerusalem bind the man who owns this belt, and deliver him into the hands of the Gentiles.’ ” 

[13] Then Paul answered, “What do you mean by weeping and breaking my heart? For I am ready not only to be bound, but also to die at Jerusalem for the name of the Lord Jesus.” NKJV (NB: All in the presence of his companions.) Now Demas' might not have been convinent with such moves. 

Maybe Demas did not have the type of "faith" Paul had. Hence, he didn't want to die, he "loved his life" as in "aion" – this period, time. So he left Paul to Thessalonica (a more safer zone to do the Gospel), others departed as well. 

Read again now: 2 Timothy 4:10 "for Demas has forsaken ["egkataleipo" - to leave in good sense] me, having loved this present world [NOT OF SIN, but time, existence], and has departed for Thessalonica—Crescens for Galatia, Titus for Dalmatia." ( NKJV) Good. 

Let me quickly ask you this question. Are you a Believer? Yes. Why are you scared of taking the Gospel to places like Iraq, Afghanistan etc? You fear Death, right? Does that mean you LOST YOUR SALVATION or BACKSLIDDEN by staying where you are now? No, it is ETERNAL, without works. You love this world and you don't want to die yet right? 

Yes. Good.... Same thing with Demas. The Bible did not say he lost his salvation! Hence, the 2 Timothy 4:10 you use is not a right verse to use while speaking against ETERNAL SALVATION. Moreover, you won't find one contradicting it, not in the Bible. Don't bring Churches in Revelation up, sit tight, learn and study. You'll understand it. I repeat, Demas did not BACKSLIDE into the world of sin. He continued the Gospel, just like others did. Only that it wasn't with Paul [it was risky with Paul: see his claims Philippians 1:20-21]. 

This was the same feeling Paul had with JOHN MARK here, but yet he was still an Apostle. 

Acts 15:36 And some days after Paul said unto Barnabas, Let us go again and visit our brethren in every city where we have preached the word of the LORD, and see how they do. 

15:37 And Barnabas determined to take with them John, whose surname was Mark. 

15:38 But Paul thought not good to take him with them, who departed from them from Pamphylia, and went not with them to the work. 

15:39 And the contention was so sharp between them, that they departed asunder one from the other: and so Barnabas took Mark, and sailed unto Cyprus; 

15:40 And Paul chose Silas, and departed, being recommended by the brethren unto the grace of God. 

So friend, you can't lose your salvation, even if you don't preach the Gospel. Losing it was never part of the plan of the salvation you got —it's Forever. But I strongly encourage that you do preach the gospel, it's power of God unto Salvation (Romans 1:16), reason you have unshakable Salvation—Eternal Salvation. I call you Blessed.

Hagios Akins