At the one week mark, I could see a slight color change in the bourbon, and I noticed a bit of a softness in the bite or heat (the alcohol in the bourbon didn't sting so much on the way down LOL!).
After 2-3 weeks, the bourbon was pretty smooth--surprisingly so, I would say. It's very easy to drink neat at this point.
For reference, I was using Benchmark for this experiment--an inexpensive but still well-liked and well-rated Kentucky Bourbon.
My observations are this: I like most bottles of Benchmark as is (I find that some bottles/batches are much better than others). The direct effect of this Viski charred wood insert was to make the Benchmark smoother, but I also felt that a little bit of the flavor disappeared. At the one week mark I tasted the Viski vs. the remainder of the original bottle (same exact bottle), and the Viski was a bit smoother, a bit darker, a little less burn on the way down, and had some very small black wood shavings in every sample that I poured. I guess the black shavings aren't a big deal, but it left me a little concerned. Yet I drank it LOL!
After 2 plus weeks, I no longer had any of of the original Benchmark to compare the Viski batch to, but I can say definitively that the Viski is at this point very smooth. Yet I feel that a bit of the flavor is missing.
So if you are a stickler for smoothness in your bourbon, this Viski is definitely the way to go. If you like all of the flavors and mouthfeel, it might still be worth a try but experiment with it on the first batch. Maybe try a pint or a half pint and compare it to the unadulterated version before going all in.