There are more than one kind of Nanotherm, which one are you talking about? The PCM+, Blue/Ice (two different version I think), XTC, or that silver EXP?
The only ones I have tried where the Blue/Ice and they were comparable to Arctic Alumina in how they worked and where kinda hard to put on but spread out under the heatsink to a fairly thin layer (did no longevity tests with it though, so don't know if it lasts a week, a year or 10 years).