Howdy scorched_porch, welcome to the board.
Sounds like you may have to add less fuel at a time. Or you may want to close off the firebox vents a little so the fuel doesn’t burn so quickly. A problem with heat retention could be in the smoker’s design or material composition. Thinner metals lose heat faster and gaps between parts will cause a lot of heat loss. Adding pre-lit fuel will recover the temperatures much quicker than adding unlit charcoal (which can cause a temperature drop until it lights).
There is a technique called the “Minion Method” which may alleviate some of the high maintenance of tending the fire. You may want to try a cheap meat like chicken on the first run if you decide to use it until you get the hang of it. The Minion Method can get burns over twelve hours long depending on the amount of fuel and smoker used. Take a look at it here to see what you think: http://www.virtualweberbullet.com/fireup2.html
You’re right it is fun. That’s one of the things I love about this hobby/sport/obsession, controlling the fire.
What brand/model offset do you have?