iPod Classic 6 turns off/deep sleep after an hour or so?

Hey, I'm not sure if this is only in the 6th gens/1st gens of the iPod Classic (Dark black metallic/aluminum front kind), but the title says it all.

My 7th gen/6.5 gen doesnt do this,

but my 5th gen iPod classics do.

So does my 6th gen.

Is this natural?

EDIT: also i have done restores on it, 0 out data, formats. etc. I don't think it is the harddrive. it has 36 retracts, 0 allocates, and 0 pending sectors.