If you have ever ridden your bike in Victoria then you would know about the dreaded thorns! They are dreadful and can even go right through a thong. Most better bike shops sell thorn resistant tubes. These are very heavy with much thicker walls along the outside. They cost twice as much as normal tubes (funny that!) but they will save you money in the long run. We use "Slime" as well and haven't had a puncture since - we ride twice a day tooooo! Some K-Marts also have them but in a very limited size range. Being thicker you MUST use the correct size. Now a word of warning for those tempted to try and ride home on a slowly leaking tyre. Don't do it or you will absolutely certainly be up for a brand new tyre. Modern tyres flex more and tend to break and bulge along the rim line.