You might be
Collecting us all - quite an achievement
Finding all the astronomical objects is very difficult (or impossible?), but stars are also often used as ratings for hotels, movies, in video games etc. Collecting the maximum number is quite an achievement.
Given that we are infinitely many
By doing a quick search, I found that the number of stars (i.e. astronomical objects) in our universe is probably greater than 10²¹. Maybe not infinite, but astounding nevertheless.
Herculean task - some would say twice so
Something with two times 12. While I'm also inclined to think that this is about the hours in the day, another reading could be the 12 tropical zodiacs plus the 12 Chinese ones, or the 12 tropical ones plus the 12 "houses" which have some significance for horoscopes, because...
Which is wrongly done for the sake of it.
... these horoscopes play a major role in astrology, a pseudoscience concerned with divination by reading the position of celestial objects at specific times (hence "wrongly done").
Nowadays a hobby, or sometimes a job
Still relating to astrology/horoscopes, some people like to read their horoscope in magazines, a few others work as fortune tellers.
Even so, lifetime's usually not enough
I read that as related to astronomy again - as mentioned above, finding all stars (celestial objects) is at least nigh impossible, and certainly "lifetime's usually not enough".
Yet in some very special conditions
Maybe the big bang?
The whole task from scratch takes a few seconds.
If you could observe the big bang, you might see all matter (and thus all stars) from scratch during a few seconds. I have to admit, especially the last two are quite a stretch.
Considering hint 3:
We see at least one star everyday: our sun. Most people can also see a certain set of stars in the night sky, but to "collect all" they'd have to go to different places/hemispheres.