1 Year - 2 Months - 5 Days. In all fairness to Tacx - this affordable seat bottle rack mount was designed to be ultra-lightweight (and it is) and probably not used by someone who averages 250 miles/week on their bike. I won't say that I abused this device... but I wasn't always gentle. And the poor mounting design (you can see the mount arms bending in the photo above where they attach to the seat) is problematic for ANY level rider. If you want the rack and the bottles to stay put - you have to really add the torque to the screws because the entire unit will slide around if you don't. This is irritating to me. I want the bottles to be where I expect them to be when I reach for them. Not somewhere else - requiring me to reach around like a person in the dark, behind my back while I am riding - to figure out where the racks had moved to.
In all - if you want to TRY a behind the seat (Time Trial) style bottle mount - at under $20 this is a great way to test it out. I am hooked, but of course I've been a TT rider most of my life. For a weekend rider who isn't going to be horribly demanding of their equipment - this unit will probably last a few years with normal use. If you are a hard-core rider who like myself - will average 10,000 miles or more in any given year - don't waste your time or money. I'm now testing a professional-quality - race-worthy seat bottle system by Profile Design - made of 6061 - T6 aircraft aluminum and rated for 6nm of torque (the rated torque for all of the bolts/nuts used in the system) - and I'll update you as I log the miles with it. I can tell you just getting the Profile Design unit out of its box that it's on a totally different level than the Tacx mount. It is 3x heavier - but in my opinion (personally) it's worth the weight penalty to know I'm not going to have to fuss with my bottle mount after every other ride. It's also notable that being one of the premier after-market parts designers for professional cyclists, the Profile Design mount is 4x more expensive.
The Profile Design RM1 seat bottle cage with CO2 mount (a convenient aerodynamic way to carry cartridges for quick tire changes).