How many times should I post about my product?
Short answer
Far more often than feels comfortable. Almost nobody sees any individual post — reach on a typical account is a small fraction of followers, and the fraction who see it and are ready to act is smaller still. Marketers assume repetition is required; developers assume saying it once has informed everyone and saying it twice is spam. The developer instinct is the one that is wrong.
The longer version
Far more often than feels comfortable, and the gap between the comfortable number and the correct number is enormous. Reach on a typical account is a small fraction of followers. Of those who see it, most are not paying attention, and of those who are, most are not in a position to act today. Any individual post reaches almost nobody.
This produces a predictable failure. The developer posts once, gets four likes, concludes the message did not work, and changes it. In reality the message was never tested — it was seen by perhaps two percent of an already small audience. Changing it now throws away the only thing that makes a message land, which is repetition.
Marketers work from the opposite default: assume nobody saw it, say it again, say it differently, keep saying it for months. That feels like spam from the inside and reads as consistency from the outside. Between the two instincts, the developer's is the one that is wrong.
The workable compromise is to vary the angle rather than the message. Same product, same core claim, told through a different problem, a different user, a different result, every time.
The full argument, with the rest of the picture around it:
Every Way to Promote a Product, and Why Developers Get Each One Wrong