I have Raspberry Pi 1B system with a Wi-Fi USB interface running one of the
latest Tumbleweed openSUSE images. After installation of the image I added
nmcli-dmenu without recommends. I disabled wicked and enabled NetworkManager.
Using nmtui I configured the wlan0 interface with a fixed IP address and the
required other network parameters. When I boot the system without a connected
Ethernet cable, the system comes up with an active Wi-Fi connection. The system
is relatively far from the AP. So when I run a ping to the default gateway I
always have a few percent loss.

When I leave the system running for a few days a see each few hours - no fixed
interval - a "Connection disconnected" with different reasons in the journal.
At a certain moment I see "Activation: failed" to the AP. The system remains at
the same location. After that NM does not try to re-establish the connection,
so the system is not reachable anymore. When I connect the Ethernet cable I
have access to the system again. Restarting the network.service re-establishes
the Wi-Fi connection, so I can pull the Ethernet cable and still have a
connection via Wi-Fi.

I would expect NM to continuously try to re-establish the Wi-Fi connection.