By design Sampler produces the same results for every N samples when you don't change your starting sample number. Unless you need more than 1000 samples, you can run your 50 and if you are not happy with the statistics, you can increase your number of samples to 100 and Sampler will only add 50 more samples/runs to the previous one and calculate the statistics of the 100 samples. You can keep this process until you reach 1000 samples. Or simply create all of your samples at once and ask Sampler not to run any case. You can later submit them in batches as you like once you get all your runs completed, you can run Sampler and it will process them as they all came from the same distribution.
thanks
Ugur Merturek