instrument conrol lights for heat/AC settings?

I have changed the light bulbs 7.00 each in the heater and ac inturment panel center console
I am wondering why they burn out in a week or so. It takes 2 bulbs if i only use 1 bulb leave the other one out it will last no problem but when the 2 are installed within 1 week one of the two are burned out? any thoughts??

2001 honda accord 2.3L 4 door sedan

I wouldnt pay 7 bucks for each... Thats some crazy price. Radio shack sells them for like 99 cents only thing is it doesnt come with the base, u can easily wind it into the base urself. It burnt out prematurely maybe due to road vibration? Make sure its completely secure on its housing. Other alternative is to use led bulbs but u have to add a resistor before it can be used. I have color changing led, its like christmas/club in my car haha good luck!