Magic Mouse / Keyboard become unpaired – fix or wired replacement?

Both iMacs I own become unpaired upon occasion after powering up. If I didn't have a wired mouse / keyboard I'd be stuck. I have no idea why this occurs but have investigated numerous times. My internet connection is solid. This happens on both computers whether hooked through ethernet or wifi.

I've been considering an iMac replacement however I'd also have to buy adapters for my old wired keyboard / mouse as I use them to access and re-pair the mouse and keyboard when the problem occurs. Do you have any suggestions to fix the issue or ideas I might consider?