The durability of Moroccan mosaic tiles, particularly those used in historic structures like the Kasbahs, is a testament to their exceptional quality and craftsmanship. Here are some reasons why these tiles have stood the test of time:

Firstly, High-Quality Materials: Traditional Moroccan mosaic tiles, or zellige, are made from non-refined natural clay, which is known for its strength and durability. The clay is sourced locally and has properties that make it exceptionally hard and durable once fired.

Secondly, Firing Process: The tiles are fired at high temperatures, which makes them dense and less porous. This process significantly increases their hardness and resistance to wear and tear.

 Thirdly, Handcrafted Excellence: Each tile is handcrafted, ensuring meticulous attention to detail. This artisanal approach results in high-quality tiles that are not only beautiful but also robust.

Fourthly, Glazing: The glaze applied to the tiles provides a protective layer that helps to resist moisture, stains, and scratches. This glazing process is crucial for the tiles' longevity, especially in varying weather conditions.

Furthermore, Installation Techniques, the traditional methods used to install these tiles contribute to their durability. The use of strong adhesives and proper spacing allows the tiles to expand and contract with temperature changes without cracking. 

Moroccan mosaic tiles are well-suited to the local climate, which can be harsh with significant temperature fluctuations. Their ability to withstand these conditions without deteriorating is a key factor in their long-term durability.

The longevity of Moroccan mosaic tiles in historic sites like Kasbahs is a clear indicator of their superior durability and timeless appeal. These tiles not only enhance the aesthetic value of the structures but also provide long-lasting functionality.