Extract from the County Councils web site:
The length of time it takes to get planning permission is affected by the completeness of the application and by whether or not there is an appeal. Generally, a valid application will be dealt with by a planning authority within twelve weeks, from the date the application is made to the final granting of permission. However, the period can vary, particularly if the planning authority seeks further information from the applicant (which must be done within the first eight weeks).
The planning authority then has four weeks from the day the further information is received to make a decision on the application. The following table illustrates the timescale involved in most cases.
Start - Notice published in paper and site notice erected
Two weeks later: Latest date for lodging application
Between two weeks and two weeks later: Application is validated by the planning authority. Submissions or objections are considered.
Between five and eight weeks later: Planning authority issue notice of their decision on the application. (Alternatively, they may request further information.)
Four weeks after issue of notice of decision: If no appeal is made, the planning authority will issue granting of permission, or outline permission, except where they have already indicated a decision to refuse.
An appeal may take longer than an application to decide, but An Bord Pleanála has an objective to decide appeals within 18 weeks of receipt of an appeal.
The planning permission for Phase 1 of Castlerock was made on 19.11.2004, so you can work out for yourself how long it takes before they are offered for sale.