hscott2hughes: Thanks, I'll investigate further. I can say without hesitation that my connection speed is crap to begin with. Watching online videos, for instance, is very frustrating - even though it's supposed to be "high speed" DSL - it's not. My old dial-up was almost as fast - but alas, that's about all we have available in this area - and we pay a fortune for it.
You can test your internet connection speed on various sites. E.g. I use
http://www.speedtest.net/
Just click on the big green "Begin Test" button, and it will check your connection's ping time (latency), download and upload speeds.
Then, based on that, you can tell what should be the maximum speed how fast you can, and should be able to, download also from GOG. Note though that at least sometimes the extras (soundtrack etc.) download slower from GOG, than the actual game installer files.
You can see the download speed on your GOG Downloader window, of course (megabytes/second). Just remember the difference between bytes and bits, ie. if the Speedtest shows 10 Mbps (megabits/second), don't expect to see 10 megabytes/second on your GOG downloader window. :) More like around 1.25 Mbytes/sec or so (with a 10Mbits/sec ADSL line; at least that is what I'm getting, theoretical maximums are not always the reality either). One megabyte per second = 8 megabits per second.
A 7 gigabyte game is quite big installer size though, it would probably take me many many hours on my home 10 megabits/second ADSL line at home as well.
Since the GOG installers are standalone, you can also opt to download them on some other place where the internet speed is faster, copy it to your USB memory stick or hard drive, and carry it home then. When I want to download a bunch of the bigger GOG titles, I sometimes download them at my work instead, as it has almost ten times faster internet connection than my home 10Mbit/s ADSL line (which is speedy enough for general use). I rather wait 30 minutes for a download to complete, instead of several hours.