Wifi disconnects very very often and is hard to reconnect

I have an Intel AC 7256 wifi adapter.

Since at least 6 months, the wifi constantly disconnects and is very hard to reconnect by restarting the network-manager service.

This is really painful.

I see lots of questions on Ubuntu stack exchange, but no appropriate answers.

Some output:
$ lspci -nnk | grep 0280 -A2
02:00.0 Network controller [0280]: Intel Corporation Wireless 7265 [8086:095a] (rev 59)
 Subsystem: Intel Corporation Dual Band Wireless-AC 7265 [8086:5110]
 Kernel driver in use: iwlwifi

$ dmesg | grep iwl
[ 2.255195] iwlwifi 0000:02:00.0: Direct firmware load for iwlwifi-7265D-19.ucode failed with error -2
[ 2.256074] iwlwifi 0000:02:00.0: Direct firmware load for iwlwifi-7265D-18.ucode failed with error -2
[ 2.274898] iwlwifi 0000:02:00.0: loaded firmware version 17.352738.0 op_mode iwlmvm
[ 2.322979] iwlwifi 0000:02:00.0: Detected Intel(R) Dual Band Wireless AC 7265, REV=0x210
[ 2.323299] iwlwifi 0000:02:00.0: L1 Enabled - LTR Enabled
[ 2.325591] iwlwifi 0000:02:00.0: L1 Enabled - LTR Enabled
[ 2.403344] ieee80211 phy0: Selected rate control algorithm 'iwl-mvm-rs'
[ 4.590676] iwlwifi 0000:02:00.0: L1 Enabled - LTR Enabled
[ 4.591435] iwlwifi 0000:02:00.0: L1 Enabled - LTR Enabled
[ 4.661301] iwlwifi 0000:02:00.0: L1 Enabled - LTR Enabled
[ 4.661923] iwlwifi 0000:02:00.0: L1 Enabled - LTR Enabled
[ 5323.096942] iwlwifi 0000:02:00.0: L1 Enabled - LTR Enabled
[ 5323.097620] iwlwifi 0000:02:00.0: L1 Enabled - LTR Enabled
[ 5323.158679] iwlwifi 0000:02:00.0: L1 Enabled - LTR Enabled
[ 5323.159212] iwlwifi 0000:02:00.0: L1 Enabled - LTR Enabled
[ 5370.610087] iwlwifi 0000:02:00.0: L1 Enabled - LTR Enabled
[ 5370.610526] iwlwifi 0000:02:00.0: L1 Enabled - LTR Enabled
[ 5370.671749] iwlwifi 0000:02:00.0: L1 Enabled - LTR Enabled
[ 5370.672338] iwlwifi 0000:02:00.0: L1 Enabled - LTR Enabled
[ 5705.684169] iwlwifi 0000:02:00.0: No association and the time event is over already...
[ 5709.274041] iwlwifi 0000:02:00.0: No association and the time event is over already...

$ rfkill list all
0: hci0: Bluetooth
 Soft blocked: no
 Hard blocked: no
1: phy0: Wireless LAN
 Soft blocked: no
 Hard blocked: no
2: asus-wlan: Wireless LAN
 Soft blocked: no
 Hard blocked: no
3: asus-bluetooth: Bluetooth
 Soft blocked: no
 Hard blocked: no

I am getting desperate for a solution, but am not prepared to try an upgrade to 18.04 at this time due to criticality of the machine for work.

Any help would be greatly appreciated.
Thanks,
BOb

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: gvfs-backends 1.28.2-1ubuntu1~16.04.2
ProcVersionSignature: Ubuntu 4.4.0-134.160-generic 4.4.140
Uname: Linux 4.4.0-134-generic x86_64
NonfreeKernelModules: nvidia_uvm nvidia_drm nvidia_modeset nvidia
ApportVersion: 2.20.1-0ubuntu2.18
Architecture: amd64
Date: Thu Sep 6 13:00:52 2018
ExecutablePath: /usr/lib/gvfs/gvfsd-network
InstallationDate: Installed on 2015-05-11 (1213 days ago)
InstallationMedia: Xubuntu 15.04 "Vivid Vervet" - Release amd64 (20150422.1)
SourcePackage: gvfs
UpgradeStatus: No upgrade log present (probably fresh install)