TDMA (Time Division Multiple Access)) is known to be an affective method for energy saving in wireless sensor networks (WSNs). However, when any slot is exclusively reserved to one node, the TDMA-based protocols suffer from low-channel utilization and high data delivery delays. STDMA (Spatial reuse TDMA) avoids these drawbacks by allowing multiple nodes to access the same time slot provided that these nodes do not interfere. The objective of this paper is to evaluate the delay performance of STDMA assuming grid networks and a random ordering of the slots in the STDMA cycle. The evaluation is performed both with a stochastic analytical model and by experiments based on a known STDMA method called VCM. Results show that the random ordering performance is rather good. A framework for STDMA applied to general graphs under SINR interference model is also presented.