I have a Maytag DE512. It takes an hour or more to dry.

Venting is not a problem.

The dryer appears to heat to ~150 degrees. I think the problem is that "cool" portion of the cycle is too long. In other words, some times when the dryer is running it will be cool, but at other times is is plenty warm. As stated above the heat seems adequate.

This leads me to believe that the problem is with the cycling thermostat. Does this sound like a proper conclusion?

If so, there appear to be three thermostats on this dryer. One on the heating unit and two on the exhaust side. The exhaust side thermostats are 150-25 and 140-20. I could not see the label on the thermostat on the heating unit. The question then becomes which thermostat do I replace?

Although venting may not be a problem did you remove the front and clean out the lint ducting inside the dryer and inspect the blower wheel? Are you testing with the exhaust removed from the back just to be sure? Does it act the same on a timed cycle and an automatic cycle?

The vent path has been cleaned from start to finish. There are no blockages or obstructions. Blower wheel was replaced about five years ago and appears to be in good condition.

Please answer the remaining 2 questions.

Willr this chick can help you, she knows her stuff, but she has no sense of humor so " just answer the questions please"

Please answer the remaining 2 questions.

Sorry. It acts the same whether it is on auto dry or timed dry. I tested the temperature at the back of the machine with the exhaust external connection removed.

I have a great sense of humor! (Look at my icon!) It' primarily satire which just doesn't translate well on the net, people think I'm being, well, mean and cranky. I was thinking "now that your ADD episode has passed can we get back to the rest of my questions"? See? It sounds mean... so pbbbbb! Moving along -

One more stupid test that is going to sound unrelated but it's not so bear with me. Remove the lint screen and run water through it. Does the water go through with little change in the stream? Does it pool somewhat on the screen and then go through? (If you require entertainment imagine I am juggling my 4 cats while standing on the back of my dog while you are doing this)

Now we have an inspection to do. Check out the condition of your front and rear felt drum seals. Are they soft and supple or are they thin, flat and kind of stiff?

Put it all back together and now we need to listen for the thermostats. This can be tricky. Start the dryer. Listen closely for the thermostat click while it is running. Is the click coming from the left by the blower housing or the right by the heating element?

Here comes the answer portion of the test!

Why did we run water through the lint screen? Fabric softener buildup on a lint screen will not allow air flow. If the water pools even a little you likely have buildup with will impede airflow causing the dryer to trip or cycle on the high limit on the right.

Bad, damaged, hard or thin drum seals will allow the air to escape into the cavity of the dryer. Again it will trip or cycle on the high limit not on the cycling thermostats or it will get hot air across the front of the thermostats not from the cooler sampling in the ducts.

Since it is working the same during both the timed and the auto dry I don't think it is either of the cycling thermostats since one of those on the duct is for timed and one is for auto dry.

This is a great dryer but it is a little long in the tooth. If you heard the click from the right you need a rear seal, from the left a front seal. I think you likely need two new seals (not the kind that balance balls on their nose) and probably need to do a little scrubbing on the lint screen.

I'm ROFLMAO and learning at the same time, I would have never thought of the lent trap prob. Very good