Best to get some soapy water and look for a leak. There is also a 4mm push fitting up near the chassis rail, that can corrode, so check this. Also check the top of the bag at the connector and at the valve block in the compressor.
As for age of your bags, that doesn't matter, its more a case of what you have been using the vehicle for, if dirt or grit gets up in the folds of the bag and hasn't been washed out then they can rub a hole quickly.