3rd day for me without crash. It might be that it is dependent on further configuration, GPU(?), or attached hardware.
I have two displays 2560x1440, both on USB-C, two external WD disks, connected to USB-C.
Energy saver settings (default): 1. hard disks to sleep when possible, 2. wake for network access, 3. enable power nap.
Hardware Overview:
Model Name: Mac mini
Model Identifier: Macmini8,1
Processor Name: Intel Core i5
Processor Speed: 3 GHz
Number of Processors: 1
Total Number of Cores: 6
L2 Cache (per Core): 256 KB
L3 Cache: 9 MB
Memory: 16 GB
Boot ROM Version: 1037.147.4.0.0 (iBridge: 17.16.16610.0.0,0)
System Software Overview:
System Version: macOS 10.14.6 (18G6020)
Kernel Version: Darwin 18.7.0
Boot Volume:
Boot Mode: Normal
Secure Virtual Memory: Enabled
System Integrity Protection: Enabled
Time since boot: 2 days 37 minutes
Intel UHD Graphics 630:
Chipset Model: Intel UHD Graphics 630
Type: GPU
Bus: Built-In
VRAM (Dynamic, Max): 1536 MB
Vendor: Intel
Device ID: 0x3e9b
Revision ID: 0x0000
Metal: Supported, feature set macOS GPUFamily2 v1