I have the 5.5g 30GB. I'm having a tough decision whether or not I should upgrade to an SD card reader - yes I get more storage and battery life, but the feedback of a spinning hard drive inside has a charm to it
Imo, use it until it breaks. The listening to the spinning disc argument got eaten by a faster ssd on another classic that I have, plus having my whole library in it, so I rarely sync new music. I tended to do so too often in the past and I screwed a Ssd by corrupting it somehow. The lesson, better leave things untouched as they work!
I was also doing that but after a while, I realised that with some good headphone (I use bose 700) the quality is very similar. I dig a little on the internet and some sound experts made a coparision with 320mps and the result was pretty similar. I switched my whole library to that format keeping the really old albums (mostly really old jazz and blues) of flac. I'm not sure if it's true that the difference is imperceptible, but now I have a ton more space.