This is one of the more interesting topics posted of late. I tend to agree with BOAC that the time you spend in the hold is not the critical factor. I believe there are two fairly distinct cases.
First is planning from the end of holding to touchdown at a single r/w destination where I simply cannot afford to go below diversion fuel before the threshold. Any extended unexpected draggy vectoring in this case concentrates the mind.
The second is where the destination is a multiple r/w destination. Here I at least have the option to burn down to final reserve by the threshold (I am assuming the case of fair weather).
In both cases it would be helpful if upon arrival at the hold we could be offered "Extended pattern approaches in use" or "Normal approach's in use" as well as the EAT. With that kind of info available I can formulate my plan with more confidence.
I think the flexibility shown at the London destinations is great but a little extra info on entering the hold could make a good system better from the drivers point of view.