caulk under all lap siding boards?

I have noticed that a lot of my lap siding boards have a small (1/16 to 1/8) crevice where the boards lap over one another -- that is where the thin top edge of the beveled siding (3/16?)goes under the the thick (3/4?) bottom edge of the next upper board.
I am painting the boards. Should I caulk all of these crevices?
(Boards have been up and sun&weather-exposed for 23 years.)
Thanks,
FACE
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Definitely not.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Ranieri wrote:

I'll second that. Any moisture that gets behind the clapboards needs a way to get out. Caulking will hold in moisture and rot the clapboards from the inside out. A general rule-of-thumb (but not always true) is to caulk vertical cracks, but not horizontal ones. Many times a horizontal seam is where water is meant to leave a structure.
Ken
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Yes - in addition, lap siding is meant to expand and contract across the width of the board - sometimes a pretty significant amount on wider lap siding.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

To Ranieri and Ken, thanks for the prompt response and I understand what you are saying and why. With the settling over the years, the vertical cracks/openings are plenty. :-)
I did close up the lower horizontal crevices on the chimney chase just above the shingles because of bouncing rain but left the upper ones uncaulked. (Mainly because I ran out of caulk -- another message. :-)) I know that the chimney cap has about an 1 1/2 inch lip-over is not watertight.
I am not "mr. construction" by any means -- I am trying to save several hundred bucks by doing stuff myself and I do a lot of "looks like" and "appears".
FACE
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.