I asked my prof last sem for a LoR, we were pretty close/friendly and he happily agreed. We met up to discuss it and he asked me to send him the details, which I did back in may. He agreed it'd be done by it's due date (mid Jan for my school committee). I can't tell if I'm just being neurotic and I know he said it'd be done but it's been like 5 months since I asked so I can't get rid of the concern that he's forgotten (I graduated and live across the country from my school so can't just go see him). Is it rude to email him about it 3 months before it's even due?