Note that Jesus makes the second appointment after he arrives and finds that the slave has been “doing so, ” that is, faithfully dispensing spiritual food. So there would be an interval between the two appointments.
لَقَدْ قَالَ يَسُوعُ :‏ « يَا لَسَعَادَةِ ذٰلِكَ ٱلْعَبْدِ إِذَا جَاءَ سَيِّدُهُ وَوَجَدَهُ يَفْعَلُ هٰكَذَا !‏