I have used ground blinds a ton over the years, for myself and those I've guided on mentored hunts. They can work great, if brushed in well and made of softer, less shiny material (usually the higher priced ones unfortunately) then they can be used to them in just one day, and often can even be hunted from that day. Closer bow shots seem to need more time to get them used to it but only a few days, in my experience.
I am moving much more now to what I'm whimsically calling wikiups, after the brush houses Apaches and others build, just my goofy name for a thick, somewhat woven together pile of brush, which I think line on the inside with a camo cloth or the ghilie blanket my kids and I are sewing up out of old camo clothes and sheets. Total time consumer and not any better, I just like it.