New Haven wrote: How long does a $100 modem last? One thing I forgot was that the longevity of the modem will depend (?) on many times you connect to the internet/day.
Any modem you buy will probably outlast your laptop. The number of times you connect to the Internet has no effect on the life of the modem. It's an entirely electronic device with no moving parts so it isn't like things wear out in it.
As with most electronic devices, provided you don't do something like spill a soda in it, the item with the greatest effect on it's life is turning it on and off. The power surges that result from turing it on and the slight expansion/contraction of the components as they heat up/cool off does more to damage most electronics than any actual use does.
Personally, if I were looking for an external modem at the moment I'd pick up the Zoom 3090 External USB from Best Buy @ $59.95. Since you mention this is for a laptop though I'd probably opt for a 56K PCMCIA modem and forget all the external stuff. You can get a ThinFax 56K PCMCIA Modem for $69 (http://www.mobileplanet.com/product.asp?dept%5Fid=4401&pf%5Fid=MP520128&listing=1) and not have to play with all the extra cables and whatnot...