How many risks are normal in a Monte Carlo simulation?

It has been suggested to me that my simulations with 400 + statistically significant risks in a simulation is taking the software way beyond its abilities. whereas I feel that in my field I expect to have an easy 1,000 risks. How many risks do you all have in a simulation?

First let me say that the risk analysis that I do are associated with EPC projects in the energy sector. I believe that the number of input variables is dependent on the project and the risks associated with project. The more complex a project, the more complex the analysis will be. The complexity will dictate the number of variables. That being said, it is important not to over complicate or simplify an analysis. Too many variables will generate an analysis that is unwieldy to use. An analysis that does not have enough variables may gloss over key risks. There really is no correct numeric value as to the input variables. I have created valid analysis with less than 50 variables and some with more than 200 input variables.