In my calculation, it will depend which songs you want it to be on board sa Ipod mo. kaya memory is not a big question.
The most important is you keep all your non-pirated songs in your computer and you just select songs then sync whenever you need.
Tips ko lang sa inyo, hangga't hinde na drain ang battery, don't re-charge. Kase it will lessen the life of the battery pag nag recharge ka na half-charged pa ito.
I hope you listen to your Ipod sa car ninyo or sa bahay using wireless connection.