Is there any reason not to keep fruits inside nalewka for too long?

In much of Eastern Europe, it is common to prepare so called nalewka. The basic idea is to take some fruit (e.g. cherries, blackcurrants) and macerate it in strong alcohol, then remove the fruit and age the liquid for several months. It is a lot like liqueur, but not quite the same. Right now, I am preparing a traditional nalewka with fruit of Cornus mas.

Is any reason not to macerate the fruit for longer than suggested in the recipe? In particular, is there any chance that the seeds would release any unwanted (poisonous?) substances if left for too long? I am mostly interested in Cornus mas because that is what I am using at the moment, but I would welcome advice about other fruit as well.

(Apologies if the question is too region-specific or otherwise inappropriate. This is my first post of this SE).