Imagine a lifeboat. Permanently anchor it at Point Nemo in the Pacific Ocean. Use whatever science you used to make yourself immortal to make the sea around you as far as you could see completely flat. Use that same science to eliminate the weather and exclude all wildlife and deorbited debris. Now climb into the lifeboat.

That would interest you longer than being in space would because you could at least dip your hands or feet into the water for a break from the sensory deprivation. But, it would only delay the slide into insanity, not stop it.

However, if you could safely land on planets, take off again, and voluntarily enter suspended animation or at least hibernate, that would be interesting.