Google Maps error from key/viewport Timeout?

After much time with user inaction, "something" happens with Google Maps' internal status that results in no future tiles being returned and the following error appearing in the Dev Tools console when a pan/zoom is attempted: -

GET http://ift.tt/2q5sNsH 
_.Nb @ js?v=3&key=AmykeyM&language=en-AU&callback=google.loader.callbacks.…:42
h @ common.js:49
(anonymous) @ common.js:49
_.Ym @ common.js:50
Xv @ common.js:159
bw @ common.js:160
_.Vv.X @ common.js:220
(anonymous) @ js?v=3&key=AmykeyM&language=en-AU&callback=google.loader.callbacks.…:127

Maybe it is a Session (or a.n.other) Timeout but, if so, how can one reliably trap the error and repair the map state?

The use-case is mainly for Web-Apps that maybe in the background for a long-time of the phone is asleep. I need continuous google map sessions spanning many days.