I'm smoking some ribs for lunch today but am having trouble sustaining smoke for linger than what feels like 20-30 minutes a a time. I'm using wood chips on my SV 24 and about every 20-30 minutes I look out and don't see any smoke. I may see a little creeping put the lower vents or the door but nothing making it through the top vent. Any idea why? I'm used to, and read here that most only need to add chips every hour. Could it be the air coming in the bottom vents? Could it be that I'm expecting too much smoke. As I write this, the smoke has stopped somewhere less than 30 minutes after I added more chips. Thanks!