nightcraw1er.488: Yes, there is some leeway allowed to give you time to mull over the purchase, and also if there are techinical difficulties. This is not however a promise that the company will exist in perpetuum just to provide a download. So whilst unlikely, if GOG stopped tomorrow and you hadn't downloaded your games, then best of luck getting them.
Safest route by far is to download things as you buy them and back them up yourself, rely on no-one.
OK, that sounds better ;)
It was just that I did object a little bit your wording in your OP ;)
On the other hand, if you got some crazy people (like me) who buy a shitload of games, because you had the original and loved it, but can´t find anymore the CD or similar AND want to be sure that it runs on modern OS´s, that´s what you end up doing, not downloading too have this little bit leeway ;)
And same can happen with a dev or distributor. Can´t remember which game it was, wanted to re-install it and had a hard time finding the patch for it again......
Ok, nowadays HD´s are bloody cheap, so in most cases no problem to have a copy or 2 to be really safe ;)