I leave for work 5 days a week at 7:45 and get back after six, and I have Bud on a twice-a-day bath schedule. His lights go on a little before six am, and I try to bathe him as late as possible- 7:30, usually. They go off around 7:30 pm, and he gets a pm bath right around then. Sometimes it's only one poop a day, and he does become totally un-trained:
1) When he's mad at me. Latest example, I got a new roommate. While Bud likes her well enough, he still went off his schedule, and pooped on the COUCH three times in ONE WEEK. (roommate said: "Wasn't aware THIS would be occurring..." 
2) When I go away for more than a day. Although, if I take him with me, there is no change at all. Kind of makes me happy that my being there is more important than which bathtub it is... although I'm sure it's only just slightly more important.
When he becomes un-trained, it takes me TWO or THREE WEEKS to get him back on!
When he's un-trained, he mostly goes in his cage, although other favorite places are the carpet in front of the bathroom (at least he tries to get there) and of course, on the couch BEHIND the throw pillows, so the humans only find it when they are relaxing after a long day of toiling for lizard funds. (Wow, I found the remote, AND something else!!!)
Today I put a rubbermaid dishpan of warm water on the bottom floor of his enclosure, just in case, with a heating pad underneath. I am not too fond of this arrangement, as it involves a tub of water on top of an electrical appliance, but my apartment inspection is today, and I am desperately hoping there will be no carpet accidents. After today, I plan to hang a heat lamp above the pan, although I do not know that this is any better. I don't want him to freeze and become immobilized in the water, but I don't want to fry him, either.
The last time I needed to show the apartment, I came home to find these odd, very evenly-spaced little marks going across my white carpet. "That's weird," I thought, "maybe it's my sneaker tread? No, too close together. Hey, it goes all the way to the bathroom, back around the room, and.... up to Bud's cage. And it leads back, across the entire length of the couch, to A GIANT POOP on the arm of the couch. " He had gone on the couch, stepped in it with one little back foot, and made a trail, a la Jeffy in Family Circus, outlining his travels during the day.
Thanks. Thanks a lot, Bud. Already hard enough to find a roommate who doesn't think we're weird. Used a whole can of carpet cleaner that day.
In short, have patience, be consistant with putting him in at about the same time and not caving in the afternoon, consider two baths a day one am one night, and if all else fails, maybe the rubbermaid thing will work. Oh, and always check behind the couch pillows before you sit down. 