I'm no expert but anything under ~18% is not going to last as long, violette, aperol, crem de mure should be stored in the fridge once opened , same with vermouth... as far as how long it will last I can't say for sure but two years would be to long.

If you buy another bottle I do like a little splash in some bubbly water on a hot day if your looking for something but don't want a full strength drink.