A puncture can happen at any time and can not only be inconvenient but can be costly and not to mention dangerous. Often it is caused by driving over debris in the road or even hitting a pot hole too hard and can happen to a brand new tyre. Some punctures can be repaired whilst other will require a new tyre to be fitted. You can expect to pay upwards of fifteen pounds per repair.
If you have a slow puncture then it is tempting to just keep inflating it every couple of days to get you through, but you are running the risk of making the puncture worse and also of the tyre becoming dangerous and causing the car to lose control.
If you notice that you have a flat tyre or under inflated tyre then you need to fill it up with air but check it again the next day to see if it has gone down again. Tyres do lose pressure naturally over time but it should not be happening in the space of a few days or even a few weeks.