After running for over half a year now, the voltage regulator got a bit exhausted and I had to add a big capacitor to buffer the current. There was also a bug in the code (string concatenation do not work well for bigger strings in node mcu), which caused it to reboot after some time, but this is also fixed now. Besides that, it is very stable and has low maintenance requirements. Also it is now part of my home automation project https://hackaday.io/project/8791-home-automation