Dating end the phone call
In general, my rule is an invitation to meet should come by the third email you send.
One common reason to delay a first date is due to an attempt to learn more about the other person. I found the first few minutes of the first date are worth more than dozens of emails.
It is important to meet early on so less time is spent talking to the wrong person and more time is spent trying to find the right one. The first date should be planned not long after communication has begun.
It is personal preference on how long to wait but there are very few reasons to delay.
Another reason to delay would be if the person you are communicating with has expressed extreme reservations about meeting people from the internet.
I once talked to a woman for two months before we met.