Yes, this is the way the milk cow mod goes on SH3. It's a SH3 limitation, not a mod fault. Beery made a "virtual" milk cow in SH3Cmdr just raising the fuel capacity of the VIIC in a predetermine period (between 42/43 if I'm not wrong) this way you don't dock at anything, so you always stay in the same patrol but you will lose all the environment which comes together of the milk cow mod. It's your choice.
Rubini.