I have been drinking whiskey for the last few years, but only in the last year or so have I been amassing any kind of what one would call a "collection". Nearly all of my bottles are open and won't be finished any time in the near future. I also have a handful of bottles that are unopened and currently out of production which I would like save for uncoming years on special occassions.

How can go about preserving my opened bottles? How will they last unattended?

How about unopened ones? How long will they last?

Thanks, guys!
Cheers