Just as a practical matter, even if you can set your phone to ring for 30 seconds before going to voicemail, most people will hang up in less time than that. Yes, studies have been done confirming this.
Granted, traditional rules of telephone courtesy may have called for one to let the phone ring 10 times before hanging up. But in the real world, circa 2016, few people will call, then let the phone ring that long before hanging up.
The chief exceptions being for calling someone known to be elderly or having physical difficulty getting to the phone. Hey, if you call a 90 year old, or someone with two broken legs, you're an ***** if you only give her 4-5 rings to answer the phone.
I'm not saying one should hang up so soon. This isn't me talking about "should," at all. This is me noting what actually is.
With a 30 second delay time before a call goes to voicemail, many callers will hang up before the 30 seconds are up. So you'll wind up with fewer voicemails, and more "call from this number, no message left" experiences. Which, frankly, some people may not mind. But there you have it.
And this is why so many carriers have, as a default, no more than 15 seconds - sometimes even less than that - before a call goes to voicemail.
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