Jesus had been preparing His disciples for His departure: first dying then ascending (John 16:17).  But the departure through death was less than three days; and leaving for heaven would be only for a while until He comes back (John 14:2-3).  In the meantime, the disciples would become apostles 'in charge of His house', with the responsibility of having everything prepared for His return, whenever that should be.  These verses sum up Jesus' teaching about the need to be prepared for God's future timetable - including persecutions and the judgement to come.  As with every undefined event, the temptation is to ignore it ... until it is so close that you can see it.  But Jesus said that will be too late.  

Jesus accepted the human limitation of not knowing so that nobody could misinterpret what He said as being the apocalyptic time-line (even though some try to construct one, falsely claiming that they know the date of the second coming).  He did not want His apostles to have the schedule until the end of time.  That would not help them as church leaders.  If the date was immediate, activism would take over from faith: if it was so delayed, there would be no incentive to keep trusting and obeying Jesus each day.  The challenge remains for us always to be ready.

In verse 34, the 'servants' are the disciples of Christ. They not only have to fulfil their roles, but they also have the responsibility to watch out, like Nehemiah's men (Nehemiah 4:17-18).  The command was, once again, to be on guard, against their own weak inclinations and the false claims of those who would be anti-Christ, even inside the church (1 Timothy 4:16).  They would be left 'in charge of the shop'; not to indulge themselves, as in the parable of the selfish tenant farmers (Mark 12:1-12), but to ensure that the harvest would be ready for the Master's return.
 
In our age of materialism, which is now a global phenomenon, our attention is easily focussed on what is immediate and how we may gain more tomorrow.  It is the wrong obsession!   We live with short term goals for they are the only ones we think we can control.  Although business claims to plan long term, such goals are susceptible to being derailed by multiple unexpected circumstances – as we have found in the intermittent sequence of global recessions.  Instead - the disciples, the church through the ages and believers in the 21st Century have a dual challenge: be prepared for long term (2 Corinthians 4:18) and treat each day as though it is the last before Jesus returns (Luke 12:40).  That day is the defining moment for humanity (Revelation 1:7).  All those who are wise will set their hearts on ensuring that He is satisfied when He arrives unannounced … except that these prophecies have alerted us to be prepared because we know He will come at any time!  So we have no excuse.