Hi, Holly!
In general, the higher the "proof" of a fermented beverage, the longer it will take to age into something mellow and pleasant to drink. That's because along with ethanol, the yeast are producing various other byproducts including higher-order alcohols and alcohol-sugar compounds. You'll often hear those things generically referred to as "fusels" or "fusel oils." They lend a harsh, almost antiseptic taste to beverages, and the higher the concentration of ethanol in the resulting mead the higher the concentration of fusels, for the most part. Fusels take time to break down into simpler, less objectionable compounds. There isn't a hard and fast rule for this since other fermentation environment factors also influence how much fusels are produced -- for example, the warmer the must the more fusels are produced.
So, higher proof meads, wines, etc., will generally take a little longer than lower %ABV beverages to become drinkable.