We sleep in the back. You can look at various trips via the link in my signature. Longest one was 21 days of which 18 nights we spent in the back of the truck.
There are no issues with odor or moisture - crack the rear window and the spoiler keeps rain and such out while still giving good ventilation. You can get cheap screens for the rear door windows if you are in a warm, buggy area.
The only "issue" is storage of stuff while you are sleeping in the back. We basically move everything in the front seats, have other stuff in 8 gal Action Packers in the footwells (see below), and leave our cooler (Grizzly bear resistant cooler) outside. If we have a ton of stuff, anything left over goes under the truck (if it's raining or in an area that gets dew in the mornings) or gets tossed in the roof basket overnight. During the day everything goes back in the cargo area.
I have a non 3rd row SR5. I assume the TRD Pro is also non 3rd row with no sliding cargo tray? If so, the trick is to remove the 2nd row seat bottoms (4 14 mm bolts, easy), fold the 2nd row seat backs all the way forward, remove that fascia panel that covers the "hump" (2 10 mm bolts), and then install some sort of riser in the cargo area to elevate it up 2.5" to make it in line with the folded 2nd row seat backs. This gives you the entire area for sleeping and makes it totally flat. Removing the seats and fascia and sliding in the riser panel takes 10 minutes and they reinstall just as fast.
My solution to the cargo area riser was to build a "pallet" out of 2 sheets of 1/2" plywood set on top of strips of 2X2" wood (which is actually 1 1/2", so this gives you a 2.5" height). Other people try and pad the area with stuff, which I think isn't as useful.
If you need more length you can move the front seats forward and place 8 gallon Rubbermaid Action Packers in the footwells, this gives you about 12 more inches for about 6.5' of length.
We then have a "full" size air mattress and bedding that we use to sleep on. The thoughtfully placed AC invertor makes inflating the air mattress every night easy. In really cold weather we use the air mattress, bedding, and sleeping bags. In really really really cold weather we use all that and run the truck as needed overnight to use the heater.
After doing it this way for a while there is no other way we'd want to do it. Setup and break down is super easy, takes like 5 minutes; we are totally self contained so we can camp anywhere including renegade camping at businesses and so forth; we are well protected in the truck with ready access to heat; and most importantly we are really comfortable.
On solo trips I use the pallet and 1 Rubbermaid Action packer and I use 2 Thermarest pads stacked on top of each other. I leave everything in the back, on one side of the cargo area, and I sleep on the other.
Since this photo was taken I have added 6 Harbor Freight D rings to the corners and center of the pallet to secure cargo. I also figured out that flat stuff can be stored under it so in those slots I have an axe, machete, and folded up tow strap. Lastly, I painted a mock up of the US ion the pallet and I note on there every trip we take so it's kind of a cool memento.
