I've been cubing for at least 5 years, so if you work it out I'd have to solve one cube about every 155 seconds, or 2:35 (rounded down). I've averaged less than ~25 seconds for the vast majority of that time, I currently average ~15 seconds.
So, basically, if I solved one every 40 seconds (which is reasonable) when practicing, then I'd have to be practicing just a hair over a quarter of the time out of the day to get 1,000,000 solves by now.
(Of course, I've probably been cubing a bit longer and the time between solves while active varies, so these numbers are just ballparking.)
And when I say I always have one with me, I mean it. When I go out, I'm more likely to not have my phone or my knife than to not have a cube. When I'm at home, there's always one in arm's reach. It's a fiddle thing, I do it while I'm doing other things and don't really think about it. I probably haven't done 1,000,000 quite yet, which is why I marked it as the most reasonable maximum, but a quarter of my time is approaching feasible. I've probably done somewhere in the neighborhood of 5-800,000.
Never said it was likely, it's just within the realm of possibility.