Samsung does produce monthly updates. http://security.samsungmobile.com/smrupdate.html#SMR-OCT-2016
"Samsung Mobile is releasing a maintenance release for major flagship models as part of monthly Security Maintenance Release (SMR) process."
I have the S5-mini and 6 months between updates sounds spot on. Daughter's Verizon S6 was just updated on Sept 27 2016.