@Nutkase 

Not sure if this is the 'solution', but all the WD drives I've gotten, and most recently the MyBook's have the WD DRIVE UTILITIES on it or a link to D/L it. I can do some things such as test the drive and do a setting for Sleep Timer.

Under Setting you'll see this:

I've turned Sleep off on all my External drives and never had one go to sleep on me on a router.

Don't have the Utilities, you can go to WDC.COM under SUPPORT and then DOWNLOAD and get the application.

Thanks for all the info guys, unfortunently that WD software does not support this specific wd p10 drive, as it just says no wd drives found.  I tried one of my other wd mybooks and sure enough that software found it and gave me and option to turn off sleep on that drive.  So I guess its just this wd p10 5gb that doesnt have a controller board or something that i can turn sleep off on it.  Guess Ill just have to use a differnt drive that doesnt go to sleep since router unable to keep it awake 24/7.......

@Nutkase 

If you connected it and it read it, and then goes to sleep later, it clearly can read it.

The P10 is a Portable drive, and that might play into it. Those type of drives pull the power from the USB port. Quite possible once it goes to sleep it loses power (doubt it though)  via the USB port? Reason I don't think so is you'd never be able to wake it up, UNLESS the router sees that as a Drive Disconnect? Suspect this is why you have to do this, " I have to login to the router and rescan the drive for it to wake up and appear on the network again OR unplug it and replug it in."

Still, take the drive to a PC and use the Utility to turn off sleep might fix it? Have you tried this?

@Nutkase 

I re-read your reply, and I missed what you said about the WD s/w.

Yes, it is not supported by it. I checked here, https://support-en.wd.com/app/products/product-detailweb/p/1537

There is a link about not seeing the drive, but it is Generic info. It does state that the USB port might not have enough power to power the P10:

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Power from USB ports can vary. The use of a Power Booster cable may be needed to provide enough power to the USB drive. A Power Booster cable is a Y-shaped cable with an extra connector that allows for connecting a USB device to two USB ports on a computer

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Well not the P10 specifically.

Sorry about my confusion.