Overclocking will only affect life of your CPU. Depending how much you overclock above the CPUs correct frequency you will non-linearly decrease its life. e.g. running at 1.1GHz will decrease lifespan and risk failure alot more than running at 900Mhz. Bare in mind the NST or any android device does not spend all time in the max possible frequency. The Governor (of which there are quite a few e.g. ondemand, conservative, performance) decides how quickly and under what circumstance the cpu frequency should change. So you may only run at 1.1Ghz 5% of the time when the NST is busy.
So from a semi-technical point of view, if I may say so, one can conclude that: it's OK to overclock NST at 1.1Ghz.