TP LINK 1750AC C8 Apparent Timeout Question

I Think my TP LINK 1750AC C8 router has a timeout setting that I would like to disable or find a clever solution to bypass.

I have my computer setup to wake on LAN remotely and i've tested that it works. I can disconnect my phone from my router's wifi and send the packet using an app and it works great... if my computer has been on recently.

Coming home from work I tested it out before arriving home and my computer didn't wake. I got home, stood in front of my computer, and confirmed again that the app did not work. I turned my computer on manually, checked the port forwarding and everything was still setup and it was, then shut my computer off. I tried again and my computer was able to wake by sending a packet through the app, again not connected to my home wifi network. See here:

http://www.tp-link.com/resources/document/Archer_C8_V1_UG.pdf

Page 40 - Connect on Demand - if using PPPoE I could set this to 0.

I'm fairly certain this router has a timeout setting where the router stops listening for packets after a certain amount of inactivity. Googling around online for this router the manual mentions this but I can only find a way to bypass the timeout if using a PPPoE connection (I am using Dynamic IP).

Does anyone have experience with this router or know how to change these settings to keep the router active all the time? Alternatively, is there an app I could load up on an old phone and just leave running that would use a tiny amount of data to prevent the router from activating the timeout? At this time I do not have a PC I leave online 24/7 that I could use.

Thank you very much