The duo were part of the England Under-21 squad which played in the European Championships until the end of June so had a reduced summer break despite not participating in the Peace Cup tournament with Villa in Spain.
But they have been virtual ever presents during the opening half of the campaign and key performers in Villa's challenge for a Champions League spot.
O'Neill believes they will reap the benefits of an unexpected 10-day break after being rested for the FA Cup tie with Blackburn and then seeing the Carling Cup semi-final clash at Ewood Park fall victim to the weather on Tuesday.
But he will still keep careful tabs through to mid May on the pair who could have an even lengthier summer if they are included in England's World Cup squad.
O'Neill said: "I think they should benefit from the break. They are preparing themselves now for this group of games in quick succession (seven in 21 days).
"Any little chance they have of getting a little break should be beneficial.
"Milner has been remarkable. We tried to give him and Gabby as much time off as possible after the Under-21 tournament and they didn't come with us to the pre-season tournament.
"But, for them to be in the sort of form they are, which is really terrific, is fantastic, and they want to play all of the time.
"Again we will have to monitor them during the second half of the season, and if there is a chance to give them some sort of break, international matches notwithstanding, we will try and do it.
"If they are picked for the World Cup, and England have a good run, it will be a long period for them.
"But for now these few days, although they weren't expecting it, should help them."
O'Neill has been linked with a move for Tottenham striker Robbie Keane while Chelsea are reported to be interested in Villa forward Emile Heskey but insists there has been no developments in either direction regarding any transfers.
He said: "I see us linked with players and some of our players are being linked with other clubs but at this minute I have nothing to report.
"There is no definite movement in either direction. Maybe like most Premier League managers, I'd probably like to keep it that way. Robbie Keane? There is absolutely nothing in it."
Villa will be looking to avenge a shock opening day of the season defeat at home to Wigan in Saturday's Premier League clash.
And O'Neill has challenged his players to show the form that has been evident since that 2-0 setback in mid August during the remainder of the campaign.
He said: "The response since that Wigan game has been great really. If you consider, from the next 19 games, we have taken 35 points.
"We have put ourselves into a position again where we are up there challenging the top four of the Premier League, are in the semi-finals of the Carling Cup and are still in FA Cup.
"We have got to try and keep it going, and if the second half of the season is half as fruitful as the first half, we will still be in with a chance.
"I think Wigan's own manager has said they've been a bit inconsistent this season and is not sure how they will perform.
"I'm expecting a tough game. They have got a point to prove and we would like to get the second half of the Premier League up and running after losing when deserving something against Liverpool."
Milner has shaken off a foot injury in time to face the Latics while Luke Young is expected to be fit after going over on an ankle in training earlier in the week.
Aston Villa 11/8, Wigan 2/1, Draw 9/4