Honestly it was quite a bit scary at first. I tried recalling what I did the previous day and whether I had moved my wrist enough or not. I then realised that I probably hadn't (didn't drive either and took a nap on the way home). Regardless, I was still very concerned and immediately started searching about the power reserve on Rolex watches. I found that the Sub 14060m (Cal. 3130) should ideally have a power reserve of 44-48 hours and if it was significantly lower, it could mean it's due for a service.
Now I'm one of those people who believe in servicing my watches only when required, you know, if it ain't broke, don't fix it, right? I am not very up to date with the servicing cost for a Sub, but started getting myself mentally prepared to shell out about Rs. 40000+ (~USD 600) - not a very pretty thought. However, before I take it to the service centre, I wanted to be sure about it and decided to test out the power reserve properly.
From what I've read, the right way to do this is to fully wind the watch using the crown and then leaving it untouched till whenever it stops ticking. So I did just that and left it on my beside table at 11:10 am. A day passed and I nervously glanced at the watch, still ticking....30 hours, all good, 36 hours, still going strong.
The next morning when I woke up, the watch had stopped at exactly 9am, which according to my calculation is a solid 45 hours and 50 mins! I was so relived and kind of impressed with the Submariner. It's still going strong as ever and ticking beautifully!