I have a WRT54GSV4 wireless router and have been very happy with it for many years. Recently it has started to drop connectivity and requires me to power cycle the unit to restore. It will come back and work fine but then will drop out again, typically when there's been no usage. There are no timeout restrictions set. I am connected both wirelessly and through network cable. All connectivity is lost when it goes down. I use Pure Network's Network Magic to monitor my network. Again, I've had no issues up til now. I've run all my virus/malware and found everything clean.
Wondering if there's a fix or a setting I'm missing (I set it and forget it so I don't know why it would just start acting this way) or if it's just time for a new router.
No way to know for sure, but these cheap, consumer-grade routers will definitely wear out after several years. The constant heat eventually takes its toll. So if it's been perfectly fine for years and nothing else has really changed (e.g., no new competing wireless signals in the vicinity), and now it’s suddenly become unreliable, there's a good chance it's just old age (yes, even routers eventually must die). But again, no way to be absolutely sure.
Only suggestion I would make is perhaps installing dd-wrt and seeing if it helps, esp. if you use it to increase the wireless signal a bit.