About the Thermal Paste on my CPU & CPU Cooler...

[PaladinAzumarill]

After nearly three weeks of building my PC, it is almost ready to be plugged in and powered on.
However, a few things that need to be addressed:

1) When should I replace the Thermal Paste between the CPU and the CPU Cooler with a new coat? Bearing in mind I used the Thermal Compound that came with this: Cooler Master Hyper 212 EVO 82.9 CFM Sleeve Bearing CPU Cooler

2) What kind of Thermal Paste should I get in the future for best performance with my CPU in terms of cooling and longevity between re-applying. Keeping in mind I have a bottle of 91% Isopropyl Alcohol that is to be used for cleaning the paste off when it gets too old: http://www.walgreens.com/store/c/walgreens-isopropyl-alcohol-first-aid-antiseptic/ID=prod6056576-product

3) Just in case, it is to be known that I applied the Thermal Paste to the CPU and, using the weight of the Heatsink to spread it out. I removed it just briefly to see where the compound went, it covers most of the upper, lower and right side of the CPU and Heatsink, except for a sizable area off to the left on both parts. Will that cause problems? Or do I have to have the paste cover ALL parts of the CPU and Heatsink? They have been installed in the Motherboard since the 3rd of July and haven't been touched since then. Would turning the PC on after such a long gap of time be safe? Or is the Thermal Compound between the CPU and Heatsink too old now and must be replaced with a new coat before powering the PC on for the first time?

Here is the CPU and CPU Cooler I use.
CPU: Intel Core i5-4690 3.5GHz Quad-Core Processor
CPU Cooler: Cooler Master Hyper 212 EVO 82.9 CFM Sleeve Bearing CPU Cooler

 

[i7Baby]

Replace the thermal paste if your cpu is getting too hot or you're replacing the cooler.

Arctic Silver 5

As long as you cover the mid 3/4 of the cpu that's OK. It should be ready to go when you are.

 

[PaladinAzumarill]

Replace the thermal paste if your cpu is getting too hot or you're replacing the cooler.

Arctic Silver 5

As long as you cover the mid 3/4 of the cpu that's OK. It should be ready to go when you are.

What would be "too hot" for the CPU I'm using? 25C? 30C?

Since you didn't mention the 91% Isopropyl Alcohol, I'm assuming that it is safe to use for Thermal Paste clean up jobs?

The same goes for not using the PC for prolong periods of time after applying new Thermal Compund, right?

 

[i7Baby]

If it's a 25C room temp, then your cpu at idle should be at 35C max and 50C max at gaming.

Use isopropyl alcohol to clean off the old thermal paste.

You can use the pc straight after re-seating the cooler for as long as you like.

 

[PaladinAzumarill]

Alright, thank you for your help.