May seem like a strange qu but with the upgrade with iTunes to non-DRM how often do u pay the upgrade? Like my?

bill is currently for like 90 tracks and a few videos. When I pay to upgrade those to non DRM does that mean I never have to pay that again or do I have to pay each time I download a new song to have it non DRM? What do u think? Please help I am finding iTunes a nightmare plus they are next to impossible to contact.