Fleet replacements indeed.
They have two A321's that are approaching 13 years old. Half a dozen A320's are over 8 years old. Half of Jetstar Asia's fleet is approaching 8/9 years old also with some being former Valuair Jets. It will be interesting to see how long they hang onto the A330's for, when you see that half the Jetstar A330 fleet is nearly 10 years old.
LCC seem to average around 10 years on their aircraft, Tiger are about to return its 2004 build A320's, some have gone with the rest to soon follow.