Just finished round 2 of Doily XII from Jan Stawasz's Tatted Treasures. I'm not doing the whole doily, just one motif from it. Just two rounds of one motif has taken me like 2 weeks.
I can't imagine how long the entire doily would take. There are like 8 of these motifs in the full doily, plus some ring/chains around the center motif. That's a lot of tatting! And you really have to pay attention to the details with this doily (and all of his designs). It's not the same size ring repeated multiple times. Each ring in a "cluster" has a unique stitch count and two or three sizes of picots. Not a pattern you can tat while vegging out. That's why I usually have two different patterns going at the same time; one more challenging, like this one, and one that is simple and repetitive. That way I can choose the pattern that suits my mood when I pick up my tatting. If I'm tired or stressed, it's the easy pattern. If I'm alert and ready to flex my tatting muscles, it's the difficult pattern.