How good is "old mono"?

[Jaiem]

How good would you consider "old" mono to be? ("old" as in unused just not manufactured yesterday).

I ask because I have the chance to buy some very high premium mono at what I feel is a great price. The spool is in good condition and sealed. It looks good, not faded. But the guy says it's 2 years old.

Is it worth a chance?

Thanks.