I called MS to get the anser to this question and am pasting the summary
provided by them below.
Summary:
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Q1- Is there a difference in file locking when accessing document for
editing over the Internet or internally?
A1- no. It will be treated the same
Q2-Clarification about Short term Locking vs. long term locking
A2-SharePoint supports two kinds of check-out:
Long term check out: This is the explicit check out. This holds a lock on
the document whether you have it open for edit or not.
Short term check out: You get this feature implicitly. If you open a
document for editing, you get a short term lock on the document to prevent
other people from editing the doc while you are.
The Office client applications refresh this lock periodically as long as you
keep the document open. Once you close the document, your short term check
out is released.
Q3- What is time period for the short term lock message?
A3- Every three minutes
Q4- What happens if the Internet session is terminated before it releases a
document?
A4- If session is terminated for any reason, WSS does not receive short term
lock every three minutes, after 10 minutes WSS will release the document