Stews - cooking time affecting flavor?

[Magictofu]

I just cooked a fairly simple oxtail stew which at first tasted great but considerably lost flavour during the later stages of cooking. I cooked it in a 300 degree oven in two stages: about three hours the first day, including some prep and browning and another three hours the second day. The meat was perfectly tender and the liquid onctuous and nice looking but it was very very bland. I had to add lots of wine, lemon juice, herbs, salt and pepper to make it palatable but the meat flavor was lost.

Is it possible that I overcooked my stew? How can we prevent such flavor loss?