A traditional looking round web doesn’t take too long to spin, usually about an hour if the spider doesn’t take breaks.
Sounds quick, but building a web is not the hard part, maintaining it is.
After a few days, the web is not only damaged from ensnaring supper but it also has lost most of its stickiness.
A spider does construction renewal, gathering up damaged threads with its front feet while trailing new silk behind.
In this way, a spider continuously keeps its web up and running.