I'm using 3 TH transmitters, 2 version 5s, and a version 4 as well. The version 4 was a "temporary" while I was getting a RangeMaster up and running, but that was several months ago, and, well, the Hamilton is still in the floor of the "evil laboratory." The TH 4 has been operating 24/7 all that time with 0 problems, and the version 5s have both been on about 14 months with NO issues whatsoever...I'm with the others in that there is a lot of difference between units, but these things don't even get warm (just the wall wart, which I eliminated, since my AM is all on solar/battery power...also, the supplied wire antennas do a great job, and believe me, I've experimented with all shapes and forms of antenna. I wrapped my 880 station antenna wire around a cardboard tube (paper towel roll) and put it on top of the shelf near the window and it seems to penetrate outside better, FYI.
Neil: I purchased a Talking House direct from Radio Systems last year. It is the New low end modified system. Also purchased the outdoor antenna system. It is mounted on the right of my front steps and grounded to the front water faucet. I get about 3/4 mile without noise and up to 1 mile with noise. I use a dbx 266XL compressor/gate to modulate. Yes distance varies with different weather conditions as all part 15 am xmitters do because of the very low power output. I am very satisfied with the system but I feel my situation is better than most because I have a ground condectivity rating of 30 here in Sibley, Iowa. I have an electrical friend that is going to build a radial underground system after the Winter here is over. This should improve coverage a bit... Good luck on your part 15 plans....
Best Regards,
Jerry Robert Mason