You are correct that most Protestants do not see the bread and wine as anything more than symbols.  There is no blessing that is ever attempted to transform the elements into the literal body and blood of Christ.  Consequently, the bread and wine (or juice) that could be stored for long periods of time prior to the observance of the Eucharist (the Lord's Supper) can be stored for long periods of time afterwards.  Additionally, if the bread or wine goes bad or if there is anything left over after an observance, they can be just thrown away.

So, some would ask if the disposing of these elements is irreverent.  To answer that, it should be understood that the elements only serve as symbols during the observance of the Eucharist/Last Supper.  Before and after, they are just regular, ordinary, "garden variety" bread and wine.

It should be noted, though, that there are some Protestant denominations that do hold the bread and wine in high regard.  Some may even subscribe to transubstantiation.  For those denominations, the practice would likely be similar to that of Catholics and Orthodox.