Looks like it's not a server-RAM issue, more like it's the game that can't really handle itself.
It goes up to about 1.7GB of memory, and by that time, it just appears to be very reluctant in responding to any console commands ...
But, running it for 6 instead of 9 hours is not really an issue, for sure there will be more interruptions, but as it's only once every six hours, no worries there!