I quit my job ~4 months ago (because I hated it, stupid big bank)...trust me, it's freaking awesome. I'll go back to work soonish, but not for lack of things to do.
Even though I love to code/work, your idea to "stop worrying and start living" and "why retire at 35" are a juxtaposition born of naivety (no offense)
I personally dont save any money 'directly' for retirement. But I'd expect people are saving living expenses for when they can not work anymore.
Edit: Indirectly is possibly my long term investments.
To answer your question about what to do after retiring at 35? I'd probably do the same thing I do now :) thats why I don't save for retirement.
Even though I love to code/work, your idea to "stop worrying and start living" and "why retire at 35" are a juxtaposition born of naivety (no offense)