liquid roof coating

In your opinion how well do those liquid roof coatings protect from leaking?

It depends on how far gone the surface to be coated is. You might get about a five year extension.

Unless you are sealing a metal roof trailer, it is stop gap at best. I wouldn’t even give it 5 years since most of the time it is poorly applied.

If you go with a product it should have ceramic.
Not saying this is good idea and is provided as info only.
http://www.supershieldcoatings.com/

Be sure the coating recommended is designed for the purpose intended. Like anything else. There are roof coatings that are simply designed to Reflect UV and protect existing functional roof membranes. Others are specifically designed for waterproofing and still have the reflective benefits. See http://quest-cp.com or http://acrymax.com for waterproofing / reroofing. and http://ersystems.com for the reflectivity and UV protection only.
Quest -CP.com has systems with Class 1 ratings and warrantys against leaks for 15 years and beyond Just a note. you cant buy a waterproof version from a home improvement store only the other .

I think Liquid EPDM coatings will be a better option. Benefits of this product is that it is very flexible in any kind of temperature, for those in colder climates it can get to 60F during the day and -20 at night.

Strange how this wonder product has not taken over??
I still like shingles and would recommend until this product has proven it self to stay with shingles.
How would you like to be the roofer who strips one of these to put on shingles one big stuck together piece to remove.