This question is a weird one coming from me, because I'm usually the type of person who is willing to help anyone at any time no matter what the circumstance. It's just how I am; ask any of my friends or colleagues if you don't believe me.
But after all the time I've dedicated to fulfilling the needs of people who took advantage of that particular character trait of mine, I've come to ask myself said eponymous question: when is it okay to be unhelpful?
For those of you who are still in school, the biggest indicator is when certain students—not everyone, as there will always be those few recurring ones—are only ever seemingly willing to talk to you or "hang out" with you if you give them what they want, whether it be opinions on their assignments, answers to homework questions, help with exam study guides, or even to just talk about school in general. That last one is what all the cool kids are about, am I right?
Of course not, which is why you should steer clear from those kinds of transactions. All these students are trying to do is instigate competition by getting ahead of the proverbial bell curve with lackeys in tow. They'll rarely ever help you in return, for one thing, and for another, that sort of business should be reserved for glass group work and exam study groups only. Don't let that extend to other parts of your life, and by extension, your spare time.
But anyway, the biggest reason I bring this question up is not just because people shouldn't be bugging you about things in your spare time.
It's also because, frankly, people shouldn't be hindering your actual workflow either.
What I mean by this is when people, especially those who don't end up becoming potential customers, start asking experts in their respective fields too many questions or for favours about anything other than the work or service at hand.
It gets to the point where it wastes the time of workers that could be otherwise spent working towards a profit that day. At that point, workers should respectfully reject inquiries about anything else other than their job—while on the job.
Don't be afraid to admit to yourselves when you've had enough of people who don't seem to understand that time really can mean money. We're all hustling and have to keep afloat, right?
It's not being rude or inconsiderate. If anything, the inquirers might learn something from you in terms of valuing their time and their own craft. Once you set those boundaries for yourselves and others and stick to them openly, there will undoubtedly be people who will respect you for it.
They say that someone's work may say something about them, but there's also much that can be discerned from said person's character by their personal protocols. It takes experience and subsequent maturity to be able to understand and eventually sympathise with that individual.
So the next time a should-be customer approaches someone regarding tangential discussions or favours in any form of business setting—yes, social media can also count—they need to put themselves in their shoes and ask themselves if that's the sort of exchange they'd want to deal with in their own spaces. Moreover, they should contemplate whether they truly appreciate what that person does for a living in the first place.
What it really comes down to is respecting everyone's time and services. People invest so much time, effort, and resources just so they could afford to service others—which in and of itself, as we all know, can be the bane of our existence.