From Apr.15~Apr.18, I kept it run “top” on the board and every 5 minutes my script sent one test.bin file(about 2MB) to board /tmp/ folder through wifi.
Now after 72 hours, its free memory is 6.5MB compared to 9.9MB at startup. Its temperature is about 65C at end(house about 24C) without heat sink. Looks good for me. 🙂