I set up my TP-Link Archer C7 (AC1750) with OpenWRT in early May.

Over the last couple of days I began to notice that several of my wireless devices were having trouble staying connected to the wireless network.  I was able to re-connect by toggling the wireless connection on/off or rebooting (depending on the device type), but the device would inevitable disconnect after a few minutes.  syslog shows messages like:

hostapd: wlan1: STA b4:ce:f6:9d:6b:20 IEEE 802.11: deauthenticated due to inactivity (timer DEAUTH/REMOVE)

Other devices did not show this problem.

A soft reboot seems to have fixed the problem for now.

Does this sound familiar to anyone?  Anything that can be done (other than just scheduling regular reboots)?

Ist this syslog from the TP or from your devices?  Which devices are you connecting?

On Client side i guess it could be some power save function of the wifi Configuration for example i used a Raspberry pi with an wifi stick which used this powersave mode. To solve the problem i had to disable this function in the config files of the driver.

On the other side your router says deauthenticated due to inactivity so it could also be an option which disconnects your devices automatically when there is no traffic via the wifi Connection. So maybe there is an option on your router to disable it.

I don´t own a TP-Link router by myself but this problem also happens on other devices too

It sounds like a configuration issue with the router.