Do I need to caulk where my vinyl siding meets the edge of my windows?
Agreed with the research you found. Most vinyl siding, if installed correctly, will not require caulk at the sides of the windows and doors. Often there is actually a separate vinyl piece installed first at the side of the window that the ends of the siding tuck into. You are supposed to leave a gap at the end of the siding pieces to permit expansion and contraction. This same siding movement is the reason that the siding comes with slotted nail holes. 



(from the familyhandyman.com web site)