Would it be better to exist forever or to never exist at all?
If I never existed I could not choose to exist or not exist since I can't retroactively choose not to have existed. Unless it was some sort of Back to the Future type thing and I can't play a guitar to ensure that my parents kiss for the first time and eventually have sex (which I'd rather not think about). Also, not existing sounds lame and boring.
Unless I had god-like superpowers I could not exist forever. At some point the Earth and the Sun will cease to exist leaving me nowhere to sit unless I could travel through space and find someplace else to sit that was reasonably comfortable. Also I'd eventually die of boredom and/or when the universe eventually collapsed.