To be fair, there doesn't have to be a memory leak in order to go OOM. That's the fastest and surest way, but there are cases where stuff just needs a ton of memory and ends up goofing up as the game goes on and on. To give you an idea of how weird it can be, I once had a completely strange crash in Sins of a Solar Empire that I didn't get - I sent them the minidump, and they got back to me saying the game ran out of memory when trying to draw the movement arrows for my fleet (it crashed when I gave a move order).
Memory management for big games is very tough, and it's not always a leak that causes the crash.
Anyway, while this suggestion isn't exactly a "solution", you can look into enabling Large Addressing Aware on the game executable. This allows the OS to give it more wiggle room (up to about 3 GB of memory, up from 2) assuming you're on a 64-bit OS. You can either search the forums and someone had a thread on how to do it, or you can also google for "3gb enabler", many games had communities who created quick scripts to enable LAA, and the process is the same regardless of what .exe you're doing it on, so they'll work for Elemental as well (you might just have to rename Elemental.exe if they expect a specific name, then change it back).
I've done this myself in earlier versions of Elemental and it helped incredibly much, I could play for hours on large maps without going OOM.
