I can't speak from experience but if by "light usage" you mean web browsing and editing the occasional document, I see no problem with this. What causes the most harm to an SD card are frequent reads/writes. You can avoid some of this issue by disabling logging activity:
You can also instruct Firefox (assuming you are using Firefox) to write cache to memory instead of writing to the disk. You can even run your entire profile in-memory for maximum speed and minimizing disk writes, With the side effect that you won't be able to pick up where you left off after you close it, that is: