The mobile agent technology is an important research area in the scope of code mobility. As part of an agent mission objective, it may exist the necessity of meeting an end-to-end deadline, although with some flexibility about the itinerary the agent should follow. The objective of this paper is to define an execution model for mobile agents that include timing constraints. We also show some simple heuristics that are able to guide these agents in the itinerary definition, considering the existence of an endto-end deadline for the mission.