Not a sweeping statement but a reasoned conclusion of its performance so far-what proof do you have they are perfoming so well? If it's the CAA figures you're going by I would hardly call a load factor between 30 and 40% sustainable.
As we saw with BRS, Eastern will persist only for so long and once the EU funding they receive goes for this route I envisage its quick demise before Eastern look at other possible routes out of MME (most likely LCY).