Colasoft has two very useful tool for testing. Colasoft packet player and Colasoft packet builder. Using these tools you can modify the packets and send it to your network for testing.
Also if some packets you have captured using Wireshark, you can save that packet in ".pkt " format and open in Colasoft player tool to send it continuously overnight.
If you use any other format other than ".pkt" the Colasoft tool wont recognize it and you cannot open it.
You can download Wireshark and Colasoft tools from below location. Both are free and are must have tools on testing PCs