It may be time to have it cleaned, even though the light went out. The reason I would lean toward checking the DPF as well, is because of the hill details you described. Now, I try not to remember things I can look up in Insite, but from what I recall, the light will go out if the ECM detects a good reading, however that reading may still be on the high side, again without knowing what your current reading is it's tough to say. You may have several codes that have not caused the check light to come on, but are thrown under certain conditions.
Just installed boost and egt gauges this weekend. Headed out on the road for a few days. I'm trying to find a time to get it into the shop. I did get a quick flash of the check engine light while bobtailing this weekend. It came on and was off again within 2 seconds. Hopefully I can swing by antrim diesel this week while im out and they can pull the code.
Well so far out on road t stat stuck closed and she got up to 220 when pulling a hill empty. Replaced that and temp went back to normal. A buddy was following me and said I was blowing blue smoke when on a pull and at shifts. Its in the shop now at antrim and they said so far egr cooler was leaking. having overhead, timing, turbo checked, and doing some egr and dpf "testing". Also doing some custom tuning on dyno tomorrow then hopefully headed out for the rest of the week.