1) The size of record also affects the processing time.
2) The max no. of possible aggregations in a cube is the product of the no. of levels of dimensions in cube. If u add levels and dimensions to a cube, the number of possible aggregations increases exponentially.
For Ex. Time dimension has four levels, Customers has five levels, and the Products has five levels. Thus, max no. of aggregations of 100 (5 customer levels x 5 product levels x 4 time levels). Now, if you add lets say a day level to Time dimension, max no. of aggregations increases to 125 (5 x 5 x 5). Now, if you add two more dimensions to the cube, each having three levels, the max no. of aggregations will increase to 1125 (5 x 5 x 5 x 3 x 3).
3) Member Properties also affects the processing time of dimensions, and hence cube.