This is an excellent point.
We were on Cozumel and the port had been closed by an El Norte. Around noon on the second day, they opened it. The good folks at Aldora called to see if we wanted to head out (duh!). So off we went.
We had a great first dive. During the SI, it was obvious that daylight was going to become an issue, since we'd started diving late and were doing longish dives. Twilight wasn't a real problem, since everybody had a light, but the group didn't really want to do a night dive (I'm kind of a fanatic about lighting, and always carry at least two on a night dive).
Profiles:
1st Dive: Santa Rosa Wall, 1:02 run time, max depth 84FSW
SI: 60 min exactly.
2nd Dive: Tunich, 57:20 run time, max depth 74FSW
We had been diving the day before, but in cenotes with a max depth of less than 30 feet.
I can provide the details of the profiles if needed.
The point is that on these dives, I was wearing a Suunto Stinger as my primary computer, with an Aeris XR1NX as backup. And 36 minutes into the second dive, at 59FSW, the Suunto had me in deco while the Aeris was happy as a clam. I knew the Suunto was ultra conservative, and I knew this was likely to happen. I had about 2200PSI left. I have no deco certifications, but I am also not an idiot. I could have just chosen to dive the Aeris. I let the DM know I was in deco, spent the next 3 minutes ascending to 40 feet (which did not clear the deco), stayed at 40 feet for 5 minutes, then ascended to 15 feet, where I shot a DSMB and hung around for the 10 minutes of deco the Suunto said I stilled owed, plus couple minutes more.
Again, the Aeris was happy as a clam throughout. But it's a console, and I prefer a wrist mount, so I didn't want to lockout the Suunto.
I've since replaced the Suunto with an Aeris Manta.
Those who reflexively decry anybody without formal deco training incurring even a light deco obligation will no doubt be bothered by my doing so. On the other hand, they wouldn't be at all upset if I'd simply ignored the Suunto and dove the Aeris.