Personally, with over a 1000 dives on Oceanic computers, I've never had this reset occur between checking my computer FO2 predive and diving, though I'm sure it could happen. I don't think it is a good habit to dive on a new day without checking the gas settings on your computer(s)
Agreed. Either way the diver should check the settings prior to the dive.
It's happened to me 3 times and it has never been a case of not setting my FO2 before the dive.
The first time, I went out on a boat, did a dive, and the 2nd dive was blown out, so my 24 hour SI started around 9:30AM or so. I went out on the same boat the next day. I set my FO2 on the way out to the dive site. The first dive site of that day was further out and so it happened that we got into the water later than 9:30. Thus, my computer reset itself to Air before I got in.
The second time, I did a shore dive on a Monday morning. Again, done and out of the water relatively early. My next dive was a boat the next day. I set my FO2 on the way out to the dive site. Again, it happened that we got in the water just a few minutes after the 24 hour clock expired from the end of my dive the day before.
The third time was the very next day. On Tuesday, my boat went out first thing in the morning, so my second dive that day ended a bit before lunch time. On Wednesday, the boat went out later, so that people could do a shore dive in the morning before the boat left. So, again it happened that I set my FO2 on the way out, but this time the boat didn't go out until 10 am. So, by the time we got in the water my 24 hour clock ran out and my computer reset to air.
In all 3 cases, it was obviously a case of unfortunate timing. But, I don't think any of my scenarios are especially far-fetched.
Now, given that you damned either way, you might as well set the default on the side of caution and call it "a feature".
I don't see how the OEM would be damned if they left the FO2 setting on whatever the diver set it to. Who is going to dive Nitrox one day and then air the next and complain that they had to change their computer setting from FO2 of 32 (or whatever) to Air?
For people who don't dive Nitrox, this "feature" doesn't do anything and is meaningless. For people who dive Nitrox, why would any of them want it to automatically change their setting after 24 hours? What would make Air a more valid setting to change it to than whatever setting it already had?
For people who don't dive Nitrox, leaving the FO2 set wherever it is means it stays on Air and that is fine for them. For people who do dive Nitrox, leaving the FO2 set wherever it is is also the desirable behavior.
This "feature" of Oceanic computers is stupid and not being able to turn the feature off - like you can with the Default 50 setting - is even more stupid. This feature is WAY more likely to cause a diver to dive with an FO2 setting that does not match what they are actually using than simply leaving the FO2 set to whatever the diver set it to. Or so it seems to me.