What's the minimum amount of ageing for an acceptable whiskey or brandy?

It may all depend on the volume of spirits you are trying to age. There is a difference is ageing and when the spirits are bottled.

How long does it take to age your own whiskey?

This is a tricky questions to answer, as it can take anywhere from 2 weeks to several years. However, small batch distillers definitely have the advantage here. When you are making whiskey in smaller batches, excellent results only take a fraction of the time they would at larger commercial distilleries. This is due to the larger surface area of charred oak to volume of spirits that can fit inside. The larger the barrel, the smaller that ratio gets and the more time the whiskey will need in that barrel. For example, a whiskey aged in our 2L barrel will probably only take a couple weeks, whereas whiskey aged in our 10L barrel will probably take a couple months, and a commercial whiskey in a 53 gallon barrel takes 2 years.

As with everything in distilling there are a lot of variables, but only one matters in the end. And that is the taste of your final product. Believe it or not, if you leave it for too long, you can impart too much wood flavor into the whiskey. It is generally best to draw a small sample from the barrel every week or two so you can see how it is aging. Once it has the color and taste you are looking for, you can transfer it to a glass jar or bottle for longer storage.

In the end, it will all come down to your own personal taste and the volume you are using.

It depends what sort of whiskey one wants. A good whiskey is aged for about 8-10 years in barrels and requires that time to reach the flavour profile required for commercial sales.

Cheaper whiskeys are aged less and it is not uncommon to find 3 and 5 year whiskey that are not unpalatable. But they are not like an aged whiskey which traditionally has "none of the fire but all of the warmth".

However if one want to convert "moonshine" into "mountain whiskey in a quick manner the trick is possibly not to use burnt wood chips (OMG!?!) but to use walnut shells or better still the walnut inner "diaphragm" that is between the lobes of the walnut. Avoid using the walnut itself as it contains oils that make the product rather hazy. These "woody" hard parts of the nut are highly coloured and flavoured (more so than the tree wood) and often easily available in areas that produce walnuts. I have made a palatable "psuedo-whiskey" in 2 months using this technique. Highly coloured and quite well flavoured from just leaving the spirit sitting on the crushed walnut shells and inner bits. A good colour alone can be obtained in a few weeks. A large hand-full of broken shells to a litre of spirit is about right.

Brandy is a wide term used for distilled wine (whiskey is essentially distilled beer). Spanish type brandy can be synthesised by leaving "moonshine" over very dry sutanans for a few weeks. Don't use dried currents as the drink turns a fetching shade of purple. If you can get a Greek product called "Petimezzo" which is essentially boiled down grape juice (like maple syrup is made) then adding that to moonshine/vodka can produce a very reasonable brandy drink, something like Metaxa. Others have used honey and maple syrup but I am not sure that qualifies as either brandy or whiskey.

I never made whiskey nor brandy, but what I have seen is people forcing aging using charred wood chips and cooling/heating cycles. This way the whiskey will penetrante the wood chips when it's heated and then leave it when it's cold (or the other way around), doing this a couple of times you can get a decent amount of "aging", of course it will not be real aging,but you will get extra flavors.

Alternatively you can store your whiskey for a couple of months/years in small barrels, the advantage of small barrels over big ones is the surface area, which much greater the smaller the barrels is.