We have the Kenmore H3s (Whirlpool manufactured them for Sears). Love the Sani cycle. My motto is if the stain didn't come out in the Sani cycle, then its not going to come out. I don't have to use my motto often :-) However, I do not recommend the Kenmores/Whirlpool for their Express cycles. I do not find they clean anywhere near as well as the Normal cycle which is just about 10-15 minutes longer. I have heard Electrolux has the shortest cycle and I want to say some models offer the Sani cycle, but I don't know how well their short/express cycles clean. Hope this helps!

The limit switch is tripping for a reason. It could be a bad switch, but it also could be tripping because the furnace is over heating. You should have the furnace inspected by a tech you trust.

Why doesn't the furnace have a filter? Tell you landlord it needs to have a filter otherwise there will be problems in the future. It sounds like the high limit switch is shutting the furnace down. The furnace may be too big for the duct work, or the duct work is too small. Whatever the reason it is an installation problem that needs to be corrected. It is wasting a lot of fuel. The service company needs to fix this problem. If it less than a year it should be under warranty.

Older thermostats used to have a degree setting, as in - turn on the equipment when room temperature varies from the setting by .25, .5, .75, 1.0 degrees, etc. Many newer thermostats have adjustable cycles per hour setting instead. I have some that are adjustable (lowest setting =2), and one at another location that is preset to 3 cycles. per hour. Remember that 3 cycles per hour can mean 10 minutes on, 10 minutes off, so that's not exactly longer cycling. Shorter cycling is harder on the equipment, so many starts and stops. Heat exchanger doesn't fully heat up in heating mode, coil doesn't fully cool and remove moisture in cooling mode. I believe equipment is happier and lasts longer with longer run times. When I'm hanging around and find my temp setting is causing frequent ons and offs, I'll change the setting to a few degrees off the desired temp (Lower for cooling, a bit warmer for heating), let it reach that setting, and then return it to the preferred setting and let it coast back to that point.