The spring punches are a good way to go. It may be the way you are operating them that is causing the failures. Some windows will break anywhere you punch them while others will only break near an edge or corner. We use these from Harbor Freight.
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Keep them packed with grease and open them up every once in a while to clean the rust and gunk out. Also solder a washer on the end for a loop so you can hang it somewhere. Watch for sales when they drop down to $1.99.
Now for the real bummer part. Thanks to the insurance agencies a lot of vehicles are being produced with laminated glass ALL the way around. That is almost a death sentence for the occupants in a submersion or fire. Their reasoning is tougher glass makes it harder for burglars to get in and steal stuff. Never mind the human element lets protect the goodies from WalMart.