due to the heat. My first wireless card went bad on me and started "bulging". A friend had another do the same thing. Both crapped out after about 1.5 years.
If you're always using the card, then there's not really anything you can do differently. Taking it out of the PC when you're not using it will help, but just expect to get another in a year or two.
I'm new to laptops, just got my first (used) one, and it does not have a built-in modem, so I have to use a PCMCIA modem. I notice that the PCMCIA modem card becomes hot rather quickly. I would prefer to leave the PCMCIA card in the laptop all the time rather than frequently plugging an unplugging it. Is this advisable? Will the heat generated damage the PCMCIA card if it is left in the laptop for hours?
I also notice that the dial-up internet connection tends to break rather frequently. I also have USB modem which works better but is less portable. Are PCMCIA modem cards generally not so good with maintaining connections, or just this particular (cheap) one that I have?