When setting off 'Render Yellow Slices' and opening the renderer viewing window, how long before it gives a realistic estimate of 'time remaining'?

I'm assuming Liquid scans the full length of the timeline, sees the work ahead, and figures out how long it is going to take.

It sometimes takes some seconds/minutes to begin estimating, and this changes as rendering begins to progress through 1%, 2% and so-on.

I often have a combination of CPU, GPU and the dreaded sluggish Movie Looks to render, and am wondering if I can take Liquid's time estimate within, say, the first 5 minutes of rendering as accurate - and also gauge time remaining by the speed the '% completed' moves along [for example if between 1 and 2% takes 1 minute, can I assume I have 99 minutes to go... or is this gauge not time-consistent?].

I'm about to render a big timeline, and have memories of the rendererer once chugging along at a good speed in the past, only to perhaps come up against a part of the timeline it finds more complex and suddenly slow down - ruining the initial 'time left' estimate and flow of 'percentage done' [and my scheduled work plans in the process].

Some further insight on how the renderer engine goes about its work on a full 1.5-hour timeline of yellow slices would be appreciated. 

Action2:

When setting off 'Render Yellow Slices' and opening the renderer viewing window, how long before it gives a realistic estimate of 'time remaining'?

Liquid doesn't test all of the possible filter combinations and store render times for each to use for estimating times. What it does do is periodically look at how many frames have rendered since the last time it looked and average that into the running estimate. If you have a 1 hour clip with a single filter on the entire clip, then the render time is pretty accurate after 10 - 15 seconds. On the other hand, if you've got 30 slices with 20 different filters, and layered filters and complex transitions, overlays, etc. then you can pretty much ignore the estimate. Liquid simply can't predict how long any particular slice will render until it starts rendering the slice.