Flat tyre help

[OpenToSuggestions]

I have just gone to do my weekly check on the car and one of the rears is at 10psi.

It has new tyres on in early 2006 and the car has done around 10-12k on them so loads of tread left, especially on the rears.

Now I have had the car for 4 years and it was 5 years old when I bought it and the spare looked new then, so am I better getting a new spare as this one is potentially 9 years old, despite looking new?

Also if I need a new tyre on the rear, is it better to buy a pair even though the rears are barely worn?
What about getting a tyre repaired?

Even though I have been drivinf 4 years, I have managed to evade a puncture for this long
Thanks

 

[IAmATeaf]

Have you tried pumping it back up and seeing if it deflates?

You've reminded me that I spotted a screw in my drivers side front which I need to get checked out.

 

[OpenToSuggestions]

Have you tried pumping it back up and seeing if it deflates?

You've reminded me that I spotted a screw in my drivers side front which I need to get checked out.

I checked it two weeks ago and it was at 30psi, now at 10psi.

I have pumped up just to see if it hold pressure to see if the valve was stuck open or something.