Are you saying that if you request the exact same model on the exact same dataset that the time varies? If that is the case I would look to system issues such as load, network traffic and number of other programs running or accessing disk and memory.   Generally a bigger dataset and more complex model, or more requested output slows any program down. Withoug details of models and datasets involved any response has to be about this generic. Many SAS procedures will go into estimates of memory usage. If your usage exceeds what the program can handle in RAM then the program spends time writing temporary values to disk and then reading them back. So disk IO can become a bottleneck.   You may want to watch some system diagnostics while the program runs to see if you are pushing the limits of the system. ... View more