This question is above my head, but you don't mention the operating system. I assume you also have a 64-bit operating system which can recognize more than 3.5 GB of memory.
What memory and how much memory is advisable also depends on what tasks you intend to do on your computer. When you start getting above 8 GB of RAM, you are talking about a very high end processor and the need for some demanding processing tasks that are probably beyond gaming. As I understand it, a less than adequate processor can have bottlenecks that do not take full advantage of very high amounts of RAM no matter the latency. I know the lower the number, the faster the RAM.
EDIT: I found this website which explains the relationship between CAS latency and RAM, but I don't know if it answers your question. Understanding Ram Timing
But Jenny100 and InlandAZ are the experts here and I'm sure they will have much better information for you.