987 Coolant Flush????

[Flavor 987S]

Have any 987 owners done a coolant flush yet? I am thinking about having this done prior to winter hibernation. Porsche says it is a lifetime coolant, but I find that a little hard to believe. My (2006 987S) fluid is now more than 5.5 years old.

What say you 987 owners?

How much Porsche coolant do we need to buy? I'm guessing 1 gallon of conc. Is plan water added to the Porsche coolant, when doing a flush? Or is distilled water used (like for a battery)?

Thanks.