150 yards is too far apart if they are pulling your posts out. On uneven ground you will need more terminal posts closer. Get on google there are some good guidelines for barbed wire fence installation.
ALSO: Keep in mind, if you pull that wire too tight and stretch the wire it cracks the galvanizing and allows the wire to rust quicker.
"You are wasting your time and breath messing with this thread, brother"....germag///
"Comparison is the thief of Joy"....Mrs. Rjcruiser