My modem is running off a battery backup, and has been on 24/7 for over 4 years now. I have never had any data loss. My router monitors my data usage, and it matches the Exede meter reading very close. My router has a very strong password, as well as the router access name and password has been changed to a strong combination.
Mine has been on nearly continuously for over a decade, only once, this month, have I had unexplained data loss and, that was a glitch during maint of ESVT, possibly because I logged into ESVT at that time, but no one knows for sure. Exede has already told me that when I hit my cap this month, all I need to do is call for a release to get my speed back - no charge. I'm happy with that, computers can and do manage to mess things up w/o the knowledge or consent of the humans using or working on them. Once in 10 yeas, I can handle that.
Markgc, the main reason is that electronic devices are most vulnerable to failure when they are first powered up, as it takes a few seconds for all the circuits to establish their operating condition, these power up conditions put added stress on the component. That is why most devices, such as TVs, are in the Standby Mode when you turn them off.