I’m a newbie building up stock! I’ve made a bunch of buccaneer bob’s black rum. I used medium toast oak spirals in glass carboys. According to package instructions 1 stick treats 3 gallons so I did that ratio. 57% abv. The package says that all oak flavor is extracted after 3 weeks

No.
Aged in the shed, temp swings 65 at night to 98 day, it was a hot Colorado summer. I find at about two to three weeks it is in fact delicious, very vanilla. One could pull the oak and drink it that way, very nice but not very oaky or complex, just a nice sweet vanilla. But you gotta check it every day cuz then it very suddenly gets astringent for a while. The change seems to,occur over just a few days. Did I over oak??? Heck no. At 4 months the astringency is gone and I can start to taste the oak. At 9 months it was perfect according to some experienced scotch snob friends of mine. It’s amazing and I drink it neat. I keep sniffing the empty glass for an hour after, I just can’t put it down! The next morning that glass still smells like barrel candy. At about 12 months the oak is mellowing, rounder, and a distinct prune flavor emerges. That’s the molasses, not the oak.
Same experience with Jimbo’s gumballhead which I basically did like UJSSM, adding the sugar but also some new grains in each batch, cornmeal mostly, starting from the AG grain bed. Same time frame but I made this to drink young while the AG ages. After 3 months I pulled some and nuclear aged it on some new medium toast spirals. It’s effing incredible!. Kept doing that and now it’s almost gone. The oak is a bit more prominent than in the rum, I think just because the rum has such an assertive molasses flavor and the UJSSM is lighter.
Currently working on some Honey Bear bourbon, intent to age a gallon or two but leave some white as well for early enjoyment. Will run gumball heads as well to keep me out of the aging stuff.
Then a batch of fancy molasses rum for drinking white, then more AG with gumball heads, then more blackstrap rum. By end of summer I should have a good stash.
So keep it on the oak and worry not!
That’s as old as any of my booze has survived so far! But now I have 2g Jimbo’s AG Malt Whisky on oak at 57% one jug med toast and one #3 char. Won’t touch it till a taste at 9 months.