How many months after asking a question on google answers, is one
likely still to get replies or comments?  Is there a half life or does
it keep going and going?

headsetsdotcom...

I'm assuming that you're still receiving email notification when
a comment is posted to one of your previous questions, i.e.
"How many people view this question?":
https://answers.google.com/answers/main?cmd=threadview&id=69883

The latest comment was on February 8th, 2003, while the question
was posted September 27, 2002, so the comment was added almost
5 months later. This has occurred largely because of the nature
of the question, which invites ongoing comments, and there is
no limit to how much later a comment can be posted. The 'Add a
Comment' bar is still functional on all questions, whether the
question is answered or expired, unless it was cancelled by the
asker, in which case the 'Add a Comment' bar will not be present.

The results you are experiencing with the question above, however,
are not typical. The majority of questions do not openly invite
continued commentary, and will not be commented on by the typical
reader unless the topic is of special interest to them. They may
add a comment at a much later time in the future if:
1.) They have had an experience relevant to the question's topic.
2.) They believe they can add significant information, and it is
    important that they do so.
3.) They perceive the answer to be incorrect (a rare occurrence,
    due to the quality of the typical researcher's efforts in 
    answering a question, and due to the tendency of the researcher
    community to provide any such corrections and additions in a
    timely manner).
4.) The topic is extremely controversial. For example, I once 
    answered a question on the legality of Federal Income Taxes,
    which was posted on August 31, 2002, and was answered on the
    same day. It continued to receive comments until September 5th,
    which I believe represents a typical 'half-life' of about a
    week. However, due to its controversial topic, it received an
    additional comment on December 15th, almost 4 months later.

Factoid: Researchers are made aware of new activity to questions
they've worked on, since these questions rise to the top of a list
of 'Answers That I Have Worked On'.

Another reason that an older question will suddenly rise to the
top of this list is when an answered question, previously left
unrated, is finally rated. While I would again estimate a typical
'half-life' of a week or less in which this usually occurs, there
have been some remarkable exceptions. Another researcher recently 
shared that a question they had answered on April 25th, 2002, was
finally rated on January 28th, 2003, 9 months later!

Questions which have been answered still have a functional 'Request
Answer Clarification' bar, so it is also possible, though relatively
rare, for a questioner to continue to request clarification of the
answer at any time down the road, even after it has been rated.
Most of our customers do not do this, since they have usually been
satisfied with the answer they received, and will rate it thereafter
and move on. Sometimes, however, a customer will rate an answer
poorly and then proceed to ask for additional clarification. You
can obviously see that this would tend to greatly reduce the 
subsequent motivation of the researcher to provide additional
information, yet, being the professionals they are, many a researcher
has gone on to provide first-rate follow-up to these requests.

Other customers will ask for clarifications before rating the answer,
and may never rate the answer after receiving the clarifications they
sought. Most will do this in a timely manner, but in the case of one
question I recently worked on, which was asked and answered on January
17, 2003, the customer posted a Request for Clarification on January
19th, and again, on January 29th, and again, on February 6th, 20 days
later. The last request amounted to a completely different question,
however, and I informed him of this.

Also, researchers sometimes add an unsolicited Clarification of the
Answer or a Comment upon coming across new information which is
relevant to a Question they recently answered. I have added such a
Clarification as many as 9 days later. This is obviously dependent
on how well an individual researcher's memory is functioning, and
their personal interest in providing additional information.  : )

I would therefore estimate that a typical question will receive
its full measure of clarifications, comments, and ratings within
5-10 days of being answered, whereas there are exceptions wherein
clarifications are requested weeks later, and comments and ratings
are tacked on as many as 5-9 months later.

Other researchers may be aware of comments which have been added
more than 5 months after the question was answered, and I invite
them to post that information in addition to this answer. Feel
free to post it as a comment, even if it's more than 5 months
from now.  : )

Please do not rate this answer until you are satisfied that
the answer cannot be improved upon by means of a dialog
established through the "Request for Clarification" process.

sublime1-ga

Search strategy consisted of searches on Google Answers for
questions, of which I was aware, which addressed your topic.
http://answers.google.com/answers/main

Thanks Sublime. Great as always!