When to have sex with someone is really a personal thing. The right time is different for different people. I am not sure if you are talking about losing your virginity, or just having sex with a new person in general. If you are talking about losing your virginity, just make sure you have done your research first so that you are not completely lost when having sex for the first time. If it is your first time with that person, I would say whenever you feel comfortable enough with them to open up to them in that way.
I would say it is best to discuss boundaries, likes, and dislikes with someone before you sleep with them just to avoid uncomfortableness and misunderstandings. I would strongly encourage using protection, but that is a personal choice. I also personally think waiting until marriage is a bad idea because you are choosing to spend the rest of your life with someone before you even know if you are sexually compatible, but it is a personal choice that has worked for some people.

Everyone has their own clock, but when I have strong feelings for someone, and it's been a while I start feeling a measure of rejection, and I will ask that person how they feel about me. If it get's interpreted as insecurity or pushy that's when I know it's not mutual.

Whenever you yourself decide. Don't go off of other people's times. Do it when it feels right and natural for you.

Before the viagra wears off?

I guess I'm just an old cynic, but I think we place far too much importance on sex and the notion that it needs to be a world-shattering expression of poetic romance on a par with Shakespeare and Donne. Sometimes it can be that. Sometimes it's a romp in the hay. Sometimes it's a satisfying one-night-stand. Sometimes it's a disaster. If you're considering doing the whoopee with someone be sure you're attracted to them that way, otherwise it's a crashing bore. Also, try to figure out whether your prospective partner would take advantage of you if you developed more than casual feelings of affection for them. Some people will use your goodwill to suck money and other favors from you. Others will get scared and dump you if they perceive that you are saddling them with the responsibility of a relationship. Some will be wonderful friends and partners. Try to figure out what you're dealing with before getting too carried away. I'm not sure what your situation is, so this is just general advice. Good luck!!!

Trust your instincts and then procrastinate a little longer.

Certainly not on the first date. I like to establish some amount of intellectual and emotional intimacy before sex, so maybe not even until after several dates. That's not to say I'm opposed to all physical contact, like cuddling and kissing.

I usually go with the flow, but prefer to at least go on a few dates with the woman before a sexual encounter enters the equation.

Whenever it feels right between two consenting adults.

what - with someone for the first time? First time in general?
The general consensus I always taught my daughter was "When it feels right for you, and when you are ready".

I honestly don't think there's a time period. I feel if the chemistry is right it can be the first date or tenth date

Float. I take a while to feel comfortable with someone, so I certainly won't begrudge anyone else for that.

If I'm interested in someone, I'm usually also up for sex. I'm not big on waiting unless I'm just not feeling it. Of course I also try to respect what the other person is or isn't feeling. It has to be mutual.

I have always just went with the flow. I’ve had it happen on the first date and not happen at all after dating for months.

For singles I suppose when you can't focus anymore on self release.
For couple I suppose a really decent romp once a month. When I say decent I mean like, the both of you don't have enough energy to go at it anymore.

As soon as ur death star is operational, it's time to fire the weapon.

So much importance and significance has been heaped on a basic human function. You can blame our religious culture dating back thousands of years.

somewhere in the neighborhood of 20 minutes.

However long it takes for you to get comfortable with the idea of having sex with someone. It’s really a very individual thing.

2 hours.

I take it on a case by case basis. If it’s going well, we’re connecting, and the chemistry is there, I’ll go ahead.

I must have been waiting too long. I've sort of forgotten how it goes.

No longer than your body and mind will bear. Seek it, take it if offered. Worry later. Or not. Life’s too short. But don’t deceive anyone. If all you want is a shag, make sure they know that. ??

No right or wrong answer. Just what works for you.