Phooey. My 800 MHz 12" iBook G3 bit the dust after I'd owned it for about two years; of course, not before it had literally every defect those models are known for, and then some. $350 down the drain.
They're cheap enough now of course that even if they don't last very long, it wouldn't be a huge loss. I don't think I'll ever go looking for another, though; I couldn't type accurately or quickly to save my life on that keyboard. Forget that infamous stench, the overbearing squish and mushy feedback they provide is the real problem.
I did, for a few months in 2008 near the end of its life, use my iBook G3 as my only machine after I stupidly killed my Mac mini while attempting to upgrade it.

At the time, it was totally doable: it took a few weeks to get accustomed to the speed drop, but I had no real complaints about its performance.
Nowadays though? I dunno, my eMac is pretty big leap ahead in specs, and it noticeably struggles with certain tasks more than I would like. I mean, I'm sure a G3 can still get the job done... eventually.
But I do approve of your quest, and am glad it seems to be going better than you expected.

I like doing the same sort of thing myself: three or four years back, I pulled out the ol' family PC from storage and challenged myself to see how long I could live with a Pentium III and Windows 98. A year and a half later, the motherboard gave out before I did.