Are there guidelines on how much free RAM a phone should have - specifically Samsung Galaxy S? I have a Samsung Galaxy S (AT&amp;T Captivate) that is rooted.  I have various ways to tweak the amount of free RAM the OS leaves on the phone.  The default is 48 MB, but I was wondering if I could actually go lower without impacting phone performance.  Are there guidelines posted anywhere, or that can be deduced based on knowledge of the Android platform?  Or should I trust that the default settings are appropriate?  I understand that when it comes to free RAM, more isn't necessarily better, but I understand that there is still a threshold that I don't want to dip below. 

I'm running a 2.3.6 Gingerbread based ROM.  For what it's worth, I'm running the Zeam launcher.
In the "linux world", what android is at its core, free RAM is wasted RAM. The system will attempt to use up as much RAM as needed. If more is needed, and there are applications that are no longer requiring the RAM it has allocated, the system will free up the RAM from that application an allocate it to the new application that needs it. 

Having less RAM available will not necessarily affect the performance. What will affect it is if it frequently needs to free up RAM on the system for other applications. meaning if there a lot of running applications that are Active, and require the RAM, then you can see performance issues. This is because the the system needs to save the state of the application, free up the RAM and then allocate the freed RAM to a new application. 

As for what a "low point" might be, I can't say. I have NEVER watched my available RAM, and never really experienced any performance issues because of RAM. for the record, I have the same device (but the T-Mobile version).