Best method for obtaining the newest firmware version for my MR6500

One question before I proceed.  What is the most reliable method for getting the latest firmware update.  I know that I originally had to use no SIM card to get the device back up and running with a new firmware version because of the boot loop problem.  Now that I have a stable device with no reboot cycles (verified overnight), is it better to just use the over the air signal with the AT&T SIM card installed or to use the same Ethernet offload method I used to originally get it running but with the AT&T SIM card installed?  My signal strength varies a bit from 2 to 3 bars when outside and does bounce between 5G and 4G-LTE at times.  Just want to know what's my best option and don't want to screw up a working device.