An aggressive value for the max-age parameter and the forward delay can lead to a very unstable STP topology. In such cases, the loss of some BPDUs can cause a loop to appear. Another issue that is not well known relates to the diameter of the bridge network. The conservative default values for the STP timers impose a maximum network diameter of seven. This maximum network diameter restricts how far away from each other bridges in the network can be. In this case, two distinct bridges cannot be more than seven hops away from each other. Part of this restriction comes from the age field that BPDUs carry.
When a BPDU propagates from the root bridge toward the leaves of the tree, the age field increments each time the BPDU goes though a bridge. Eventually, the bridge discards the BPDU when the age field goes beyond maximum age. If the root is too far away from some bridges of the network, this issue can occur. This issue affects convergence of the spanning tree.
Take special care if you plan to change STP timers from the default value. There is danger if you try to get faster reconvergence in this way. An STP timer change has an impact on the diameter of the network and the stability of the STP. You can change the bridge priority to select the root bridge, and change the port cost or priority parameter to control redundancy and load balancing.