If you application is such that it has to do lot of allocation/de-allocation of large size objects (>85000 Bytes), its eventually will cause memory fragmentation and you app
A program always bombs on OOM because it is asking for a chunk of memory that's too large, never because it completely exhausted all virtual memory address space. You could argue that's a problem with the LOH getting fragmented, it is just as easy to argue that the program is using too much virtual memory.
Once a program goes beyond allocating half the addressable virtual memory (a gigabyte), it is really time to either consider making its code smarter so it doesn't gobble so much memory. Or making a 64-bit operating system a prerequisite. The latter is always cheaper. It doesn't come out of your pocket either.