I generally don't do spreads, but I recent had some ES short options I sold go in the money and I took the contracts rather than rolling out or closing the trade. So, I had these 10 short ES futures. I figured while I figure out what my next moves in the portfolio would be, I'd offset them by going long 10 ES contracts in September, just to cover my ass. (I also write a few OTM puts and calls to scrape some premium while I pondered my next move.) I noticed, though, that every day I was receiving a $50 credit for my offsetting ES contracts, almost like a carry trade. Made me wonder: Is this a low-risk trade, short front month, long three months out, watch the spread narrow as the front month expiration nears? I assume the spread can widen and I'll pay $50 a day, but under what circumstances and conditions, generally? Also, how much margin am I eating with a spread like this?