Original H100 and H100i was both in service until very recently, from 2012 and 2013 respectively. Now only the H100i remains in service, this was because the original H100 was just way too loud now (it also has REALLY bad PWM whine from the controller and the tubes were feeling more stiff than when it first got here, suggesting it may possibly crack at some point) and no other system was going to make use of it. So it got recycled away.
The H100i (original, not the updated versions) suffered from wear on the rubber caps surrounding the tubes, but apparently doesn't impact on the safety of the unit as the tubes are barbed. As apparently they were for cosmetic purposes only. Of course I didn't trust a word they said and moved it from the top of the case to the front (after some modding) and taped up the areas where wear was noticable. Still in service now as it's only cooling a 3570 at 4Ghz (barely 60C at full load). This unit was used the most (pretty much 8-12 hours a day, every day of the year for 5-6 years straight), then finally going from the main rig, to the rig under the TV for living room use (where it has more light activity).
But both went the distance and have done well I would say, especially compared to some other stories we hear. In short, if nothing happens soon after purchase, your AIO likely would last beyond its warranty period.