I’ve never really enjoyed talking on the phone and always resort to communicating with people online, however, there are a few (very few) people I can chit-chat with endlessly. @lucillelucillelucille is one of them. We talk on the phone for no less than an hour a day. Sometimes two and once in a blue moon we push it to three or four.
To answer the question, I guess it’s when leisurely talking on the phone begins to interfere with important tasks and errands you should be achieving throughout your daily or weekly routine. It’s not difficult to get carried away. I have plenty of times. You have to monitor yourself. But if not, I don’t see much wrong with it. It is a form of human contact and I happen to value it, especially when a good friend of mine, like Lucille or @perspicacious lives out of state and I want to hear their beautiful voices! :D