Our MH is 8 years old. Last 4 1/2 we've lived in it 100-120 days. We cook in it and all of the things previously mentioned. We run the Fantastic Fan almost continuously and always try to keep a couple of windows slightly open except in the coldest weather.
We also travel with four cats and three dogs. So, our odor load is significant. Last month we had someone in our MH replacing the blinds and she commented on how some RVs smell of animals and ours didn't. We aren't clean freaks.
I notice that you live in East Texas. Humidity might be a contributing factor. We are out west were the humidity is very low. I would think that humidity could hold in odors.