I'm at the 500 hour mark, but i see people all the time here claiming of have played for 2000 plus hours. My question is what is it that keeps you hooked on the game. Just for me to get to the 500 hour mark i had to come up with my own incentives, like save the MQ for the perfect character, which i just did two days ago. Now, what i'm doing to keep me baited in the game is starting to read and collect books. I've played almost every character type and when i become overpowered i'll swicth to using the characters weaker skills to level up at mid level to keep things challenging.
Now with all this stuff i've done i want to wrap my mind around how other people can get 1500 more hours than me and still have the drive and addiction to play the game. For the recorded, i rarely FT, when i do its cause i forgot something or dont feel like spending 3 hours trying to buy an ingredient.
Thus, what is it you do cause i want to breath new life in my game

Have you done EVERY SINGLE QUEST, including DG? Even with fast travel, that's 350 hours MINIMUM. If you NEVER fast travel, then there's simply no way that you've visited every single location and done every single quest there is to do. Unpossible.
Work on your skills - especially smithing and enchanting. That will require you to gather ore, smelt it and work it. You will also have to fill soul gems. You will also be able to improve Alteration magic thru transmuting iron into silver and gold, and then smith gold rings and necklaces that you can enchant.
Have you run more than one character? If not, try a new character. Start switching up races - try Orc (great fighters, if a bit homely.) Try different 'classes' - for instance, be a bosmer thief and/or assassin and get really good with sneak, lockpick, archery and pickpocketing. Or be a breton or (if you dare) a high elf, and specialize in Magic. Drive those skills up and add perks. Since you'll be getting into combat, you'll want to drive restoration, destruction and conjuration up, fast.
I have yet to reach level 1000. I've done every single quest (including all the DG and HF stuff.) I'm about 956 hours, level 74.
If you're strong enough, hunt giants and dragons. Clear out every single bandit lair and every single falmer lair. DG changes the falmer lairs somewhat and has helped keep them fresh.