Long Term Whisky Storage

I've been drinking Bourbon and Rye for almost 10 years and recently got into Scotch, but I usually only ever have 2 or 3 bottles in the house, all of them open and none of them lasting more than 3 or 4 months tops. So far I've only purchased something new after emptying a bottle that I already have. After recently getting into Scotch I've thought about collecting a bit more and saving special bottles long term. I am wondering how well whisky can keep in the long run under various conditions. I have done some research already and I know several factors can help preserve whisky - keep out of direct sunlight and high heat, tip bottles periodically to wet the cork, the less air in the bottle the longer it will last, etc... I'm a little concerned though because I've heard conflicting numbers on how long you can safely keep whisky under good conditions.

An example of why I'm asking is that I just bought a bottle of GlenDronach 21 Parliament to celebrate the birth of my first child (expecting in a few days) and I thought it would be nice to have a dram after my son is born and then put it away and only have some on special occasions, maybe even saving it for 10 years or more. I saw a video by Horst where he preserved an almost full bottle of Speymalt using the ParaFilm sealing paper and I'm thinking about purchasing some, but how long could I expect whisky to last after resealing it? Also, once the bottle is down to maybe a half or a third is it time to give up preserving it for much longer due to the oxygen exposure or am I good to keep holding onto it?

Another scenario I was concerned about is if I start to increase the number of open bottles that I keep in order to have a wider variety to drink from. If I increase the number of open bottles I keep I'll definitely be emptying them less frequently and so they could set out open for quite a while. Does anyone have experience keeping an open bottle in good temperature and out of sunlight for a long period of time. How long would you expect your whisky to stay safe like that once the bottle is emptied out a good ways?

Last question would be how long can I expect sealed bottles to last? I've seen numbers reported in articles, but I was wondering if anyone has experience with their own whiskies in some of the scenarios I mentioned to confirm. Sorry for asking so many questions in one post. I just want to make sure I'm not running into a risk of wasting whisky from buying too much and holding onto it as I am very new to collecting. Thanks and Cheers!