I've had my no-frills Thetford TC 25100 for about 18 years now and the only time it leaked was when I didn't put the top unit back on the bottom unit properly. Only did that once!!
If it ever fails I plan on replacing it with the another 2.5 gallon capacity unit. The larger units might sound good initially but 5 gallons of waste is awful heavy, especially when trying to empty the tank into a 4" dump-tube!!
I have it sitting on top of a custom stand to get the seat-height back up to something reasonable and there is storage in the stand for bowl-liners, tank chem, and toilet paper. Stand and toilet slid into a cupboard when not in use.
