My experience about making the ETR shorter
At first, let's see what should we do to make a photo online. Shooting, adjusting, uploading, keywording, then waiting for reviewing. Each of these work can take a lot of time but why only ETR bother you? Because you can do nothing to reduce the ETR but just waiting. Changing you point of view, you will find that you really can do something while ETR. You can shooting, adjusting, uploading, keywording, it will make you feel that the ETR is shorter.
My experience and advise is that keeping shooting and uploading, a lot. Then you will find you have a lots of Unfinished Files to deal with. So that you have no time to notice the ETR things. It make you feel the ETR is shorter.
There is another tip. If you put some pics in the Unfinished Files for a while, such as a week, then you finish them, you will find that the ETR is very small or n/a, even the pic is under review directly.
Photo credits: Jin Peng.