So, am I guessing right? DA PA ranking getting consider based on number of years it's registered for, as a major factor?
No. The number of years for which a domain is registered was one of those hypothetical factors floated in Google's historical data patent, as I remember, that Google probably patented because it was there and no one else had claimed it... but, since then, a number of Google spokespeople, Matt Cutts for sure, has explicitly said that length of registration is not currently a ranking factor. Google doesn't use everything it's patented. Superficially, length of registration does suggest a degree of commitment to a domain. It certainly wouldn't make good sense to register a slash and burn domain for ten years. On the other hand, registration term by itself it would be flawed as a ranking metric, and I think Google knows that. Eg, it might well make sense to register a blue chip domain only for one year, say because you're checking out the registrar.
Now obviously Moz might perhaps correlate length of registration with its DA and PS numbers anyway, and superficially the correlation might hold... I really don't know. But correlation is not necessarily causation. A causal relationship between rankings and domain age, IMO, would more likely be due to ongoing efforts put into building a good site (old domains likely have had more work done on them than two month wonders), and less about what kind of deal you've made made with your registrar. As noted, Moz, in coming up with DA and PS, isn't privy to the actual Google algo factors.
Other factors cited, like number of your Alexa ranking, make me wonder how much some of these factors you cite really matter. This Alexa ranking fetish is something we dismissed in the US quite a few years ago.
I think gut level assessment of whether a site is informative, engaging, and useful would be a lot more accurate than any of these numbers, which are iffy at best... but such an assessment is harder to squeeze into a number and assign it a label, and would require some independent judgement which many "SEOs" lack the experience to make. And as martinibuster points out, one number generally doesn't hold for all situations.