On steemit, if you do not claim the rewards in your wallet, after a certain period of time do you lose them? Or are they just there forever until you claim them?

My hubby was offline for over a month at least and when he logged back in, there were no rewards at all, even though he is on steemauto to upvote people. Although he is also new and only has an SP of about 10 right now. Can you earn curation rewards at all if your SP is that low?