Costello, who joined the Red Army in 2005 as elite development officer, admits lessons were learned after a disappointing European campaign and isn't putting it past his troops to replicate the 2008 success.
"This year has certainly been more favourable than last year," said Costello.
"It was a unique situation where we didn't make the knockout stages of the Heineken Cup. To be knocked put in the group stages was very disappointing last year, so it has been a massive improvement.
"The message has always been keep the faith, standards have been there in training, we've perhaps been a little bit unlucky in some games.
"But it's only the halfway stage, it depends what happens around April and May that's going to decide how successful this season is going to be."
With a squad to rival the very best in European rugby Munster's willingness to blood youngsters has questioned but Costello, who is also Munster 'A' head coach, quashed that notion and claimed playing with the best can only help the fledgling stars.
He added: "The reality is because we have so many established internationals in the side, the likes of Paul O'Connell and Ronan O'Gara, it takes a little bit longer for those youngsters to break through.
"You see the likes of Peter O'Mahoney and for me they are going to be better players for having been around experienced players and competing for positions.
"I think that's where Munster is unique. You have to be displacing an established international."
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