Lots to consider when using used barrels. Like the smaller barrels age out the wine must faster due to much more surface area. Depending on size of barrel, time has a big multiplier. The smaller barrels are much thinner, so what's in it may oxidize faster, plus more evaporation (angels share). Next is how long has it been empty? Once they start drying out, micro organisms, bacteria, mold, you name it can get in the barrel wood. Once a barrel becomes empty it needs to be cleaned and then filled with water and changed often. Not sure whiskey tasting wine would be good, but I guess only through experimentation will one find out. If you decide to try it, let us know how it goes.