Alright, don't flame me for my headcanon-ed timeline... But I felt like between sidequests, planet story, and main story, this is how long we were running around in our roles. Not including ops and whatever because they're a pain to try and figure out, sometimes.
Vanilla Ch1:
Warrior - 8 months to 1 year
Inquisitor - 7 or 8 months
Knight - 4-ish months
Consular - 5 months
Smuggler - 9 months to 1 year
Trooper - 6 or 7 months
Agent - 6 or 7 months
Hunter - 6-ish months
Vanilla Ch2:
Haven't played a couple of classes through Ch2 in a while, but it's maybe 2 months, tops.
Vanilla Ch3:
Only gonna mention classes that I finished Ch3 on...
Warrior - 10 months, maybe a year(?)
Inquisitor - 8 months, with at least one of those spent on the last couple of planets and the Kaggath and whatever.
Hunter - 8 or 10 months
Smuggler - Somewhere around a year, I think...
Interlude:
Black Hole - 2 days, maybe 3
CZ-198 - 4 days at the most
Ilum - A week-ish
RotHC:
Makeb - 3 or 4 days
Oricon - 2 days
SoR:
Forged Alliances - a month or two
Rishi - (another month or two after Alliances, imo...) a couple of weeks
Yavin - about a week
Ziost - maybe a day or two?