No, not necessary. I ignore it. The only time I do is when I get tonnage or if I sight a Task Force. When my alloted time is up within the confines of the area I get a new location to go to. At the end of two patrols, if I don't get targets then the message tells me to patrol the area at my discretion. If I run out of torps they tell be to get back to base. TC do not miss. I went 1024 and the pop up message asking me for what actions to take. This goes for surface and air threats.
TM has really improved a lot. I hope RFB does the same.