Tyre Replacement, one or both?

Evening ladies and gents.
I have just booked in my FA for its 24000km service. The Odo reads 24,278km at the minute and in the three odd weeks until the service I expect to run up at least another 1000-1200kms with some commuting and a couple of weekend rides planned. Last service was at 19500, so thats about right.

My question however is about tyres. I got a set of Pirelli Angel GTs on at around 10,500kms. I am absolutely delighted with them and they give me all the confidence I want in the wet or dry. The front is looking worn, particularly on the right side and is probably due replacement. The rear has a bit of squaring but has tread left on it both in the middle and the sides. Most of my riding is my 140km round trip commute, ergo lots of highway riding.
So assuming I should not be complaining about 14000kms odd out of the front tyre at least, am I better replacing them as a pair or persisting with the rear until its completely done. I can get a pair for $390 NZD, not sure about the single price.

I have in the past sold part worn tyres to fellas doing burnouts and drags at the track.

Thanks in anticipation of measured responses

For the price of piece of mind, I always replace tyres in pairs. 
I can't see the logic of having a lovely new hoop on the front and a square rear. That feeling we have all experienced, the new bike feeling,  with two new tyres can't be beat.  
Just my opinion.  

Generally speaking its cheaper to replace both than just the one. I got a pair of PR4s fitting a couple of years ago for $400. The next time with money a bit tight and only the rear needing replacing I paid $320 for just the rear and then 6 months later $220 for the front.

Dealers often do good deals for a pair

Bosco15 wrote:For the price of piece of mind, I always replace tyres in pairs. 
I can't see the logic of having a lovely new hoop on the front and a square rear. That feeling we have all experienced, the new bike feeling,  with two new tyres can't be beat.  
Just my opinion.  

I tend to agree with Bosco.... 

I used to just do one at a time; but prefer to do both at once these days: because yes, a new pair makes a big difference.
The "saving" that you think you are getting from an extra 20% use of the front can be swallowed up by increased price anyway; as well as time spent going to the tyre place twice instead of once.

And... more tread on the front is surely more important.

I'm looking forward to trying the Angels once the Michelins have had a bit more wear.