How to make LEGO unbreakable I would like to build a LEGO model which is unbreakable.

What is the best approach?

I am not looking for just glue here.

EDIT:

I don't just want to strengthen the bond between the bricks, but the model as a whole. The level of force to withstand is in the area where it would actually break a single brick.

/EDIT

Has anyone tried the kind of spray on film you can use to protect your car from bumps? How does these kind of product react with LEGO plastic?

Also important is that whatever I would use should not add a thick layer on top of the LEGO, it needs to retain it's original size to some extent. A millimeter or maybe two in some places could be ok.
This is really nearly impossible unless you have a lifetime supply of super glue.

A good structure using Technic LEGO bricks will provide better support and a lot more "stick" to each other, making the creation less breakable. Building the structure in which the strongest side will take the most hits/pressure should be an excellent way to make the model unbreakable. Joining a Technic skeleton with other bricks should improve your model's durability. Technic and regular LEGO bricks create the best possible way for models to not fall apart.

Overlapping bricks (longer bricks preferred) like bricks can make a strong support for each other. Each piece helps each other support a piece, having no weak points unless layered unevenly. 

Try making your models fall and see where they break most often. The place where they break off is probably a weak point and needs more support or the pieces used are just too weak for the job. Replace/rebuild to improve the overall structure of the model. Of course, long bricks are preferred as the pressure is more evenly placed, making the hits seem pitiful against the strong model.