Really depends.

My first one ,kudzu, took me over a year because i lacked the focus and did not want to grind mats. So i took it easy.

Astralaria was next and i found it so pretty i wanted to have it so grinded the achievements for it and it took maybe half a year.

Was lucky when i crafted aurora last year, since i did the druid backpack already when season 3 came out. Used the mats from the return to achievements so there was only achievement grind. Took me maybe 2 months. Vision aswell.

End of last year i made the first gen3 leggy with the staff of aurene and primordus variant. Maybe one month for that since you have all the mats from finishing EoD mostly.

Last month i made Exordium which i just bought most of the mats for which was a lot. But it was done in a few weeks because of that.

Depends on what generation and if you have a precursor or not (or the money for one.)

Gen 1 is all about having the stuff. I already had done map completion in my main and had a gift of battle purchased ages ago for if I ever wanted a legendary. But I played engi so there was like zero reason to have one cuz they don’t show basically ever, and wasn’t a fan of any anyways. Eventually I got a precursor drop of the uh warhorn, so I made that and it basically took like… an hour… cuz I had everything and just bought some mats and etc.

Gen 3 Ive made a few: A few days of WvW for battle. Map completion of 4 maps (or lamp lighting of 4 maps) is a few days(maybe a day for each map). Getting imperial favours is maybe a day (maybe multiple if you’re doing a lot back to back and have nothing saved). Rest is mats. Plenty long term mats that can save you from directly purchasing by doing stuff daily/weekly: ASS weekly purchases and strike CMs, runestones daily across echovald. Fishing daily for ambergris. Laurels, extra provisioner tokens, etc. can help for mats for gifts. Overall, if I’m actually dedicated and have some good maybe 2 weeks. If not maybe 2-4 months to kinda passively get one.

I guess it technically took me 10 years? I didn’t really think about legendaries until recently, where I made the Quip. What took the longest was the achievements, but it was hilarious. Had to travel around Tyria and prank or throw pie in peoples faces!