Does Thermal Paste "stop working"?

[w1llyg]

Hi guys,

Ive had my PC for two years now, and recently I have noticed my PC is outputting a lot of heat. I occasionally I clean my case out of dust which I have done today. I have seen the temps drop dwn 5 degree but its still not as cool as it was two years ago.

2 yrs ago.
~33 degrees idle, ~42 load.

NOW
39 degrees idle, 50 load. Prime 20mins.

I dont understand why the temperatures have risen. Does thermal paste perish over time?

I want to get it as cool as possilble before I start OCing. My room is normal temp.

This is the set up of my PC. Any cooling suggestions appreciated.

 

[w1llyg]

Yup, I took the radiator off and used the hoover to suck whatever dust was in there.
Knocked a couple of degrees off idle but nothing on load.