"If you normally eat a reasonable meal at a restaurant and then one day they offer you an all you can eat deal do you stay there eating constantly till, ala Mr Creosote, you explode?"
Actually, at an all you can eat, I have been known to eat more then I normally would, considering that as I spend about 15+ hours a day at a comp, eating a decent meal is rare.
However, when it comes to internet speeds, currently I have a 16mbps/2mbps connection. On average, I may use only a small percentage of said connection, BUT if im attempting a large transfer between systems, I expect to get my 16mbps connection ( in reality, due to transfer rates between systems, congestion, and other junk, it may be lower, however anything less then 13mbps/1.5mbps and I complain).
I do NOT expect, that the 2 or 3 days a month I actually use the connection to the fullest for a few hours , to suddently find myself stuck at 2mbps the rest of the month.
Now for example, if I had a 150mbps/100mbps connection, if i needed to upload a file, I would expect to get a decent speed as thats what im paying for, so I should get it.
http://www.speedtest.net/result/319044780.png my connection, done at time I was writing this reply, while also connecting to my work. When ive seen it below 13mbps/1.5mbps a quick call to my cable company, and I am usually back up to speed, or in rare cases (about once a year) I get a new modem from them.