Time between meetings and use of 久しぶり

Generally speaking, how much time needs to go by before it would be natural to use 久しぶり?
Is 2 weeks too short? A month? Where is the line?

Does frequency affect the usage of 久しぶり? As in, you meet regularly every 2 months, so you wouldn't say 久しぶり?

Example situations:

1) You regularly go to a gym and get to know several people there, but because you sometimes skip days as do they, after seeing them 3 times a week for a few months, a month goes by without seeing them. The next time you meet, would you say 久しぶり?

2) You only rarely go to the library, say once every 3 or 4 months, and someone you know works there. That is the only place you see them. Do you say 久しぶり every time?

I generally use 久しぶり if its more than a month. 久しぶり means "Long time no see" or "It has been a while." How do you define "long time" or "a while" is definitely matter of one's preference.

I believe another variable that you could factor in is how often you are suppose to meet this person. For example, if you see the same person regularly, let's say every 2 weeks. You don't say 久しぶり everytime. However if you were expected to see this person every week but this person misses the meeting or class and there is 2 weeks of gap then you could say 久しぶり after 2 weeks. Therefore I believe you can't always put defined time frame to the word 久しぶり. It deals with how often you are expected to meet this person and the time gap.

• I'm curious if you have any perspective on usage of 久しぶり vs. しばらく. I lived for a while in the Tōhoku, where I heard しばらく almost exclusively. Later I moved to the Kantō, where I heard 久しぶり all the time instead. Amusingly, this roughly correlates with the stereotypically more-restrained north-MIdwestern US word choice ("it's been a while") vs. the kinds of expressions used in more southern climes ("it's been forever"). Are you aware of any similar geographic differences in Japanese and word choice (久しぶり vs. しばらく)? Commented Nov 2, 2018 at 16:20
• Sorry for the late reply. The reason for it is because I don't know the answer. I'm certainly not the right person to ask for the geographic differences in Japanese language. My take on 久しぶり vs しばらく (there is something similar called ご無沙汰しております) is お久しぶりです can be used in either business settings or casual settings, which is probably reason why many people in Kanto use these. しばらくです is less likely to used in the business settings and hard to convert it to Keigo. (*note) Therefore, I don't think it has to do with geographic differences but rather how formal and informal this expression is. Commented Nov 5, 2018 at 16:28
• *note: hard to convert means it makes a sentence unnecessary long or unnatural) Commented Nov 5, 2018 at 16:30