I think there is a good chance, that 1.35v for 24h will reduce the lifetime of your CPU. I have a 4770K and I will not go above 1.3v for daily operation because for a 22nm CPU that's pretty high and I have already seen reports of chip degradation. 4.2 with 1.2v would defenitely be more healthy or maybe 4.3 with 1.24v if that works. Your fan will also run much more quiet I guess
Btw, which synthetic test did u run? You need one using the new AVX2 instructions because there is an extra automatic voltage bump in the CPU when using those instructions (recent versions of AIDA64, Intel burn test or Prime95 use those instructions).
If you want very quiet operation or you want to overclock (you would need a 4670K model though), then u need an aftermarket cooler, otherwise not. You can just try the default cooler and if it's too loud you can still replace it afterwards.