Quick answers at PeterWhieldon.co.uk
Decanting wines… Good question! Generally speaking, you should not decant wine into a decanter. At least not initially.
I believe that all wines should be enjoyed from the first sip to the last. Most wines will taste a little sharper if you drink them immediately the bottle has been opened. As you pour into a wine glass, air circulates and as you continue to swirl the glass, the wine becomes further aerated and the taste changes to a more mellow, or buttery taste.
If a wine is so sharp that it needs decanting then it can be decanted and left to rest for a while (usually about 20 to 30 minutes is sufficient) before pouring, but if after decanting you find that the wine has aired too much and lost its ‘fruit’ there is no going back!
If a wine has been left in the bottle too long and has lost its fruit or bouquet, decanting will not make any difference to the taste so no harm at all in decanting in this situation.
So I think that generally, wine can be left in the bottle and poured directly to the glass. An exception to this rule is if a wine needs to be separated from its sediment. Decanting is very helpful in this case.