Question about dust + thermalpaste.

[IAmAkiro]

I know the questions might sound wierd, also sorry if I'm not in the right place at the forum.

But my GPU is starting to get dust and I am soon going to clean it, when we move, but I had a question my GPU hits the 65-67 degress in stresstests and I wanted to know more about the thermal grease and how it works.

1. Should I worry over the grease on a 1070 ROG STRIX, after 8-9 months? 

2. What temperatures can the grease hold to?

3. How often should I maybe reapply new grease?

4. My old 680 hitted over 70 degress in a lot of games after cleaning was around 3 years old, is that really enough time for the grease to dry out? it hitted around 90 degress in Dead by Daylight on lowest settings. 

Reason I ask is because I'd be sad if I had to take my card apart after 2 years of using it.  

[IntMD]

1. Not normally

2. Much higher than yours is going to

3. When your card starts overheating - basically, quite a while

4. Sounds like a possibility with those temps

[IAmAkiro]

I also know it's summer Soon, but I'm more afraid i can't get the dust out properly. I'm not really a great techie, only the things in Windows and parts to pick, not assemble and that