In another thread, there are strongly expressed opinions in both directions on the question of root account expiry. (Opinions are based on security on one side versus user freedom on the other.) The expiry date can be changed with the chage command (not a typo).
Setting expiry to tomorrow’s date, I rebooted and the cron job worked, i.e. the USB power control was ‘on’ rather than ‘auto’ after reboot.
Aside from the security aspect of non-expiring root account, there is the question of battery consumption if USB power is on by default even when no internet connection is in use. On an L5 turned on but doing nothing except waiting for calls or texts to come in, and starting at a battery level of 85% in both cases, the battery level dropped in 30 minutes to 81% with ‘auto’ USB, whereas it went to 79% with ‘on’ USB.
[EDIT 16:50 EST 20240218: The other thing that bothers me about enabling the root account is that there are four root commands already in /etc/crontab. They seem to be something to do with testing the device before shipping (and presumably before the root account was disabled). Since the device is shipped with those commands apparently not to be run, it might seem that they should be commented out by anyone who re-enables the root account. However, I just don’t know enough to be sure that it is appropriate either to let them run or to comment them out.]