I have checked for leaks and found none. Door gasket is super tight. I stack my wood in a criss cross pattern for good airflow. The stove has always burned like this since the day I put it in. Maybe the draft on it is to strong, it has 28 feet of stainless liner in it, i don't know. I will load it up with about 3/4 load, if I try to fill it completely it tends too run to hot. I will bring temps at stovetop to about 450-500 then close the air control, leaving just a crack open. It simply will not burn more than 4 hours. Stove top temps during operation are between 500-600 degrees. I reload between 300-350. Secondary burns are inconsistent, sometimes I get them sometimes not. Whether the secondary burn is on or not, the burn times are the same.
Everything I have bolded, is your problem. Lets take this in steps:
1. Load the wood all same direction. If you can load with the splits ends facing front to back or North to South as they say, you will be able to pack the wood in tighter and higher. Criss cross is just giving it too much air, and also leaving too much air space that could be filled with wood.
2. Before you blame the stove, and exchange it only to have the same issues, learn the stove and the best ways to burn it.
3. I have 27' of rigid insulated liner, and yes it drafts hard sometimes, but I never get less than 12 hour burn times, unless I don't do a full load and use soft wood. So liner height should not be an issue.
4.Load it up full with LARGE splits. Criss crossing with smaller splits will only last a short time, and it not the way to achieve a good long burn. Criss cross is for short, hot fires, as you are experiencing.
5.Try closing the air leaver completely, you won't constantly have secondaries, nor do you need secondaries constantly. If the stove rises to temp and heats the home, this is all that matters. Close that puppy all the way down and see what happens. Just know the difference between smoldering splits and glowing burning splits. These stoves burn top down. If it reaches cruising temp and holds, your heating and burning efficiently. and I guarantee it will last much longer than 4 hours. If it smolders and temp drops, open the air up again and get the temp a lil higher, then close back down again. You need to experiment and learn the stove and how to get the best burn out of it. Not just load it, get a temp, close it up some and expect it to magically do as you wish. Note, if you wood is not dry as it should be, your stove top temps will be lower and the wood will smolder, and you will need to leave the air open and lose burn times & temps. Again with 28' of liner, you should be needing to close that air lever all the way.
6. Patience is truly a virtue with wood burning. Try letting is burn down to 200 or 250 before reloading. Again, with good dry wood, you should be able to have just a nice level NOT THICK AS HELL coal bed on the bottom, and load a new full LARGE splits load on the coal bed, and obtain what you seek to achieve.
Large splits , then fill in with mediums and smalls. The larges will consume firebox air space, and keep the fires from hell from coming and will also bring the longer burn times.
Before getting rid of a stove for issues that are not the stove, but the operator & most likely wood, put the time in to learn the stove. As I said, otherwise you will be complaining about the next stove, and the one after that, and the one after that. etc. etc.