How long is an unopened bottle of drambuie good?

I emailed the company and they sent me this reply:

"Hi,

Thank you for your inquiry regarding DRAMBUIE Liqueur. As per your request, please be advised that DRAMBUIE has an indefinite shelf life. The liqueur's quality does not change provided that the product is kept unopened, stored in a dry, cool location (avg. 10-20 C) and protected from direct sunlight. In addition, quick variations of ambient conditions should be avoided, especially from cold to warm.

We hope you find this information useful and would like to take this opportunity to thank you for your valued patronage."