What I noticed from the sobriety community (specifically alcohol), it is important to make promises to yourself 'one day at a a time'. There is a presumed danger to tying too much of your ego to the duration of your sobriety. I am not sure if it is scientifically proven, but if you relapse the assumption is you would rather have a psychology built around making the right choice today and not one built on pride of a large number of consecutive days of sobriety.
Yeah. Because relapsing happens to almost everyone. And even if your "sober streak" resets to zero you haven't lost your motivation to stay sober, the experience of being sober (and knowing you can cope), and the tools you've learned. You're still in a better position than before, all you need to do is get back on the horse. Fixating on a streak just makes it harder to do that.
I've always wondered, if someone has a drink the week before getting, for example, their 10 year pin, do they not get the pin, or is there some kind of duolingo take-back?
Personally if I drank once or twice within a 10 year period I'd still count it as 10 years sober. There's a big difference between a one-off 'lapse' and a 'relapse'. And I suspect a large number of '10 year sober' people have had the occasional lapse and just don't want to admit it.
Put it another way, is 10 years with a few lapses worth significantly less than 10 years completely sober? Of course not. It's still a huge achievement. So why punish yourself?
If you think it's worth lying about having 10 years, then why bother lying about having 10 years?
In practice, milestones are more for sharing one's experience than for attaining an award. And if you slip up, telling that truth is honestly more helpful for the other person struggling to stay sober than lying to them about having 10 years.