Try this solution guys.
In origin game properties, set game launch option to x86. In your bf4 game folder, set bf4x86.exe to windows 7 compatibility mode if you run windows 8/8.1.
So far played the game longest without seeing any memory leak.
I found a slightly better solution in Windows 8.1 - you can keep the game in x64 but follow the following step: In your bf4 game folder, select 'Troubleshoot compatibility' and set bf4x86.exe to compatibility with Window 8. This seems to be keeping memory clearer. I'm getting 38% usage in game now. All very tidy.
