Thermal paste after it has frozen?

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Just a short question I've been wondering:

Once a thermal paste gets frozen, does it lose its thermal characteristics?

More detailed description:
At some point I inadvertently placed my Noctua NH-U12F's thermal paste syringe on the outdoors storage room (must have been there for about a year or two), and the temperature can go as low as -30 celsius in the winter.

I was thinking that considering it's probably a highly synthetic compound, it might not be affected (or maybe -30 C isn't even enough to freeze it?). But also precisely because it's a compound, I fear that it might have frozen first only partially (higher melting-point alloys), and afterwards the rest (lower melting point). And once it thaws out, it might not melt back to its original "structure"/"mix".

From an outside inspection, it looks normal, there's no visible un-evenness, air/liquid bubbles or anything like that. It also spreads like it used to, I think. If an outside person saw it, he wouldn't be able to tell that it's been frozen at some point. But I just don't want it to start boiling if I put it on the heatsink.

Furthermore, it was bought in 2006, so a follow-up question would be: does the thermal paste lose its characteristics over time? There is a cap on the syringe, so it doesn't come into contact with air, at least. But now it's a 9 years old thermal paste, and if I end up using it on the new rig, as well, it will probably stay untouched for ~5 years more.

So, as I'm building a new rig atm, I was now wondering whether I would have to invest in an extra thermal paste syringe, as well? Or is it perfectly safe to still use it?
 
Mine came in the NH-U12F package. It's a generic (no labels) clear plastic syringe with white paste and a small blue cap, like in here:
http://www.dvhardware.net/reviews/noctua_nh_u12f/2.jpg
(from a DV Hardware review of the NH-U12F)

The NT-H1 wasn't yet even available when I bought my unit. But yes, there's a high chance that it's actually the same stuff (or similar in characteristics) that they use in that one, as well. It's probably not BETTER than the NT-H1, at least.

Hmm, from the looks of it, LN2 is a liquid nitrogen solution? If that is OK without any special thermal pastes, then I think I should be OK with regards to the temperature. The recommended storage time is a little discouraging, though. Seems like I'll have to invest in a new thermal paste, then.

Thanks for the input. :)
 
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