The importance of a good base and correct amount of sand

The base provides the strength for the pavers, and enables them to remain flat over extended periods of time and through harsh weather conditions.

The base materials are usually made out of crushed stone, such as, gravel or limestone. The important characteristic of the base material is that the crushed stones have sharp edges. This will allow the base to compact together better, to form a strong foundation.  If your paver installation has the proper base the odds of failure are slim.  

Another area of failure is the sand setting bed that the pavers are laid on.  It is important not to have over 1" of sand or it may be viable to movement.  Because of the fine aggregates in the sand it can move when wet and cause settlement in the pavers above.