The EPG can update any time of the day, not limited to daily re-boot. I've noticed that even after I have permanently deleted recordings, the real big savings in HDD space appears AFTER the daily re-boot.
IMHO, the daily re-boot was instituted to avoid the common practice of many Dish subscribers back in the earlier days of Dish, specifically with the first STB's and later the 3900's, etc. or pre-ViP equipment, meaning 1990's and early 2000's boxes.
For some time, the 1990's boxes would NOT immediately show video or play audio when powered on. Instead, a black screen with a message stating that is was accessing--if I remember correctly--or something like that would appear until video and audio could be output. The boxes were waiting for the key in the digital stream to allow access. This can take several seconds to longer than 30 seconds and even up to a minute. This really bothered people, so some subscribers would--either on their own OR from advice from installers/retailers--just leave the box on at all times 24/7. I found this to be an incredibly common thing for Dish subscribers back in those days, and I had family who did this, too. Eventually Dish fixed the long wait for video and audio problem by sending the key at more frequent intervals allowing a picture to appear in about 5 seconds, but people still had the habit of leaving the STB on ALL the time 24/7, sometimes just to have TV in the background or fall asleep to watching TV, and this created a problem:
Well, quite a few customers would call to complain about their Dish system behaving strangely or not functioning correctly. Most often this is because the subscriber had NOT put the STB in stand-by for like WEEKS or MONTHS. The solution was to put the STB in standby and wait several minutes, and this would allow the STB to get the firmware updates it should have gotten a long, long, time ago. I know many who had to do this as they just watch TV a lot and just leave the box on and shut the TV off. So, to elminate this problem of a bad habit, Dish designed the future boxes to re-boot itself once a day, or not too long after if the viewer wanted to continue to watch TV or record.
The daily reboot does a lot, as Scott stated in a previous post, and we all know that a re-boot can fix all many of little problems, and for Dish STB's it is a good "re-fresh," for the new day, but the daily re-boot also ensures that STB's will get the latest firmware update as soon as it is available to be pushed to that STB, and this prevents a lot of costly calls to CSR's and ensures a a better Dish experience to the customer.
The one thing I DO NOT LIKE about the H3 is that if one has NOT had the opportunity to put the box in stand-by, then after about 36 hours a message pop's up stating that "Something is Wrong" because I have gone to long without putting the box in stand-by and the H3 WILL re-boot itself and you can NOT stop it, so I have interruption in what I was watching LIVE because I was not recording it, and the box just dumps and re-boot. That is so irritating. It drives me crazy! It's like an Airbus Airliner that leaves the computer in ultimate control and not the pilot.
Daily re-boot means the end of leaving your STB powered ON at all times of the day and night for days and weeks and months.