Brrr... your temps are a lot colder than ours. I'm not used to this yet. My husband says come March you'll think it's t-shirt weather.
As long as you aren't burning wet wood and choking it way down to where it smolders for long periods of time, your risk of gunking up your chimney is very low. Just keep doing what you're doing for a month, then take a look at the chimney and make sure its working.