Recently the dryer has not been drying clothes in 1 hour. They are taking about 2 1/2 hours to dry. Sometimes the ignition lights up gas and creates a flame. Today the ignition did not light up and the clothes just tumbled.

What part needs replacing:

Ignition

Electronic control board

Thermostat

There a 2 things that would make the ignitor not come on here. 1 being the sensor on the side of the flame tube, and the ignitor itself. If I understand you correctly, you are saying the ignitor did not lite today. Here is what I would do. Unplug the dryer, and take the 2 wires off the sensor, and put the terminal ends together, and put tape around them so they don't hit metal. If the ignitor comes on, and the gas comes out, replace the sensor. Do Not Run the dryer that way. This is for testing. If the ignitor does not come on, replace the ignitor. Let me know what happens so I could instruct you further. Tom ApplianceEducator.com