Time Pressure Good - Too Much Pressure Bad
The problem I have found is that if you have too much time pressure there is insufficient time to reflect and this leads to what I call a "short-circuited experiential" (see http://www.simulations.co.uk/kolb.htm) where the learners do not reflect or conceptualise - they just oscillate between experimentaion and experience.
But having said that, I feel that cognitive (work) load needs to increase as the simulation progresses (see http://www.simulations.co.uk/DESIGN07.HTM) and, although largely predefined. for simple business simulations, this can be controlled by increasing or reducing the time between making decisions. For one simulation (Product Launch) that I have run many, many times, I found that some groups started quickly and then found that the problem was harder than envisaged and slowed their decision-making. In contrast, others started slowly with detailed discussion and planing but then speeded their decision-making with both groups completing the simulation in the budgeted time!