The feeling of always wanting newer possessions?
Solution 1:
avaricious
showing an extremely strong wish to get or keep money or possessions:
-Cambridge online.
An avaricious person is very greedy for money or possessions.
-Collins online
My Oxford Advanced Learner's Dictionary (9th edition) describes it as...
desire for wealth
and the same dictionary describes wealth as...
a large amount of money, property, etc.
An avaricious person seeks money, and possesions, just to have them.
The noun is avarice.
Solution 2:
Materialistic? The desire to possess tangible objects.