My Klose doesn't have gaskets, and it doesn't leak anywhere unless the exhaust is closed. I always keep the exhaust wide open, and temperature control is done with adjusting the airflow at the firebox vent. There will always be swings in temperature with an offset when you add a stick of wood or open the cooker. The dryness and density of the wood also affects how large the swing in temperature is. I have some very dry wood I keep on hand that I can use when I need a quick boost in heat. Once my cooker is up to temperature, It will hold steady temp for an hour or so depending on the number of sticks I'm using.
Cooking BBQ is something I do to relax, and tending the firebox is just a part of it. There are plenty of BBQ rigs out there that are set-and-forget if that's what a person is seeking. It's just a matter of choosing what fits your needs and lifestyle.
48" Klose Backyard Chef, _ Primo Oval XL
Stealth-Grey Thermapen, Maverick ET-732