From my oldcel experience-
20-21 you should be damn worried and doing everything you can ..an all out assault on your virginity..will probably end in failure but it's not time to give up yet..
By 25 it's time to give it up, you are way past your prime and any effort you put into getting into a meaningful relationship will end in failure and heartbreak..just forget about women at this point.
By The time you are 30 nothing has really changed since being 25.. it's a meaningless milestone, you should have given up 5 years ago and been happy being dead if that's how you want to handle things, or way ahead in other persuits because you gave up on women a long time ago...
Don't keep chasing the impossible because it will keep you from acheaving other goals in life..