My cat has been gone for a week is that too long?

He was an outdoor cat then we moved and tried to make him and indoor cat but every week or so he gets really weird and I mean weird so he does his best to get out and has done so three times before this. The first time he was gone for a day and we caught him in the yard and the second he was gone for like three days and we caught him in the yard again but the last time he was gone for four days and just came back on his own up to the porch while we were sitting there. He has been gone for a week now and we leave food out for him and something sure is eating it but I'm afraid something has happened to him or when he comes home he doesn't stay because we aren't outside like he has no way in so he leaves. It's getting cold and snowy so it worries me even more because shouldn't he want to come home to get out of the cold? What should we do?