I bought EU4 in June, four months ago, and Steam says I played 542 hours. Some of this is just the game open on my PC and me doing something else like taking care of the kids, but still I play about 3 hours per day in mean time.
I did the following parties:
_ two with Portugal to start, the second ended in 1821: took me one month and a half
_ one with Mali for their special achievement about colonizing South America: done in one day (1444-1651 in game time)
_ 7 with Dai Viet for their special achievement before 1500, done in 3-4 days
_ one with Genoa to have Protected Market (without DLC): 3-4 evenings to play from 1444 to 1655
_ one with Moscovia, gaining several achievements (Royal Authority, Relentless Push East, Grand Duchy, All belongs to Mother Russia, In the Name of the Father) before using Siberia to conquer Japan (for The Rising Sun achievement): two weeks from start to end, 1444 to 1809 in game
_ one with Austria, failed attempt to build HRE, ended in 1607 after achieving The pen is mightier than the sword achievement: two days
_ one with Hesse, from 1444 to 1767, started with objectives to have their special achievement for mercenaries but also to become Emperor. Finally I became protestant, lost the League War and finished by destroy the HRE and create Germany: two weeks
_ one with Nassau, for the Electable! achievement, ran from 1444 to 1517 in some hours
_ current game with Poland started on 10 October and now in 1655. Aim is to have A king to rule (done), Winged Hussards and Poland in Space.
I play in speed 5, except some critical war moments where a one day difference may matter between life and death for a big part of my army/fleet, but that is rather rare. And always in Ironman, so no rollback to add more time to games. I also don't restart, except with achievements with a given goal date, like the Dai Viet one, when I think I'm too late. If things go bad I change objective (Hesse losing the imperial throne to a very early king death at the wrong time, then losing the League War by an inch) or I try to recover (I ran into two bankruptcies with my Genoa campaign (both to avoid annihilation by the Ottoman when all my allies decided not to defend me...)).