It is important to set a timeline at the beginning, but also to keep in mind that political events beyond your control may force you to change it. For example, your target audiences may unexpectedly change, an opponent may turn into an ally, or a strategy which seemed adequate to begin with may not yield the expected results. Advocacy initiatives require continuous and careful monitoring, since your strategy will need to adjust along with the political climate. Advocacy activities will often need to be revised and re-directed. In short, it is important to remain flexible.
One reason that flexibility is so vital is that valuable windows of opportunity often come up suddenly; a policy change which you thought would take five years to achieve could be accomplished in a few months, if the public takes an interest in your policy issue. If a new government is elected, your issue could rise to the top of key policy-makers' agendas. In contrast, a policy that you thought could be easily changed may instead encounter unexpected opposition and require a longer time frame than you thought at first, this is because the policy environment is unpredictable and it is probably best to schedule conservatively, so always include extra time for unanticipated events. If, in the end, you accomplish your goals earlier than expected, your initiative will seem even more successful in the eyes of members.