So, for anyone wondering..

I cant go to much into my project due to NDA's ect however I can report this.

Aircraft:
DJI Phamtom 4 2018 built, everything was standard except the power source - we where using a tethered battery to the ground (we where only flying a 20ft due to weight of cable, and just to be safe and crash was going to happen)

The old girl hovered there (winds around 15km/hr) for just over 37hrs !!! And even then it didnt crash, it self landed due the controller getting a critical error (cant go into that). That's crazy... we are going again next week once we resolve the error we are getting (its to do with our project)

That's 37hours.. bloody awesome !!

Hello there Renames. Good day and thank you for sharing these information with us. Have a safe and a happy flying always.