Run cycle is almost three hours on my 6 or 7 year old machine and it's not always cleaning very well. Any suggestions?

First try cleaning out the machine with a gallon of vinegar run through the wash cycle several times. Turn off the water. If you have a manual dial set machine, try to set your machine to come on, at the longest cycle, then add the gallon of vinegar. Stop it before it drains out and reset it to the longest wash cycle again. After the third time you try this, turn the water back on and let it finish the cycle. Alternatively, use a product called Lemi-shine to wash the tub and wash arms out. It may take 2 packages. In the future add 1/4 cup of vinegar to the wash cycle to keep it clean. Secondly, check the float and make sure it is not coated with gunk. Remove it and scrub it out with a strong detergent and hot water. Check to make sure the drain is not blocked in the bottom. To do this, remove the lower tray and put it aside. Then remove the flat plate looking cover ( check ofr a knob that might be screwed down to keep it in place, and remove that.Sometims they screw in reverse.) and look for hidden objects that might be blocking the drain. You can use an old toothbrush to scrub into the corners and around the drain screen to get out the gunk. Then replace everything and give it a run.