How long does it take you to...

[RykerNightshard]

1. Complete the community centre/Joja form
2. Level 10 in all areas
3. Reach the bottom of the mines
4. Complete Qi's challenge
5. Full mastery
6. Unlock Ginger island
7. Fully unlock Ginger island
8. Unlock the walnut room
9. Get all walnuts
10. Reach the top of the volcano
11. Get 10 million all-time gold
12. Complete all special requests
13. Complete all walnut room quests
14. Build all obelisks
15. Build the golden clock
16. Craft everything
17. Cook everything
18. Ship everything
19. Catch all fish
20. Complete the museum
21. Read all books
22. Full hearts with everyone
23. Eat all stardrops
24. Complete all achievements
25. Reach perfection
26. Get 100 million all-time gold

For me, it's

1. 4 years
2. 3 years
3. 2 years
4. 4 years
5. 5 years
6. 4 years
7. 5 years
8. 5 years
9. Too long (thanks joja)
10. 4 years
11. 5 years
12. 4 years
13. Absolutely not
14. Never
15. Too expensive, not worth it IMO
16. Too tedious
17. Ditto
18. 7 years
19. 5 years (frickin octopus)
20. 5 years
21. too long
22. too long
23. too long
24. Never
25. Never
26. STAY AWAY

 

[Nonak]

1-2. a little over a year
3. 1,5 seasons
6. Usually I have everything needed to repair the boat by the time I complete the community centre so right after I complete it.
8-9. Year 2+
10. The second or third day after going to ginger island
14-15. Y 3+
25. I only did it once and it was Y 7 (first play through) and then I got close to it on another save in early Y3 but then I accidentally deleted the save.
That's how long it takes me in vanilla. Recently started playing modded stardew and now i don't rush stuff, prioritizing exploring new things added by the mods, so my progression's slowed down a bit in some aspects.
Also I skipped a lot of points on your list just because I don't remember by what time I complete them