Sixty days is the minimum because Texas has a mandatory waiting period of that length. As a practical matter, that timeframe is seldom realistic.
Divorce is a process – not an event. After having made the decision to pursue a divorce, it is natural to want the matter wrapped up promptly. It will probably not proceed quickly enough to suit you. It will simply take as long as is necessary for your spouse to accept the realities of divorce and focus upon resolving the issues that are part of the process.