As a recommendation, I would allow more than 4 lines every 10 seconds, which is what your code appears to be currently allowing.
The default timing for the /play command is one line per second, which, for most channels/networks is good to prevent flooding, and it's still a good speed for most people to be able to read the line being displayed before the next line is displayed.
If the network uses UnrealIRCd, you might consider using the +f channel mode. More details on this are available on UnrealIRCd's documentation website.
