Fescue seed is germinating! When do I mow?

I combined two seed brands (mostly Fescue). I've got very dense shade on my front lawn so I needed something built for that. They all say different lengths to mow!

I think I'm just going to wait until it's really long, like 5+", and then mow the highest setting. Really need the root system to take hold.

Scott's Dense Shade Mix:
30% Endeavor II Tall Fescue
30% Faith Tall Fescue
30% Gazelle II Tall Fescue
10% Wendy Jean Creeping Red Fescue

Jonathan Green Black Beauty Dense Shade Mix:
30% Dakota Tall Fescue
25% Carmen Chewings Fescue
15% Eugene Creeping Red Fescue
10% Frontier Perennial Ryegrass
10% Stanton Perennial Ryegrass
10% Deepblue Kentucky Bluegrass

I mixed it up because I really wanted to throw the kitchen sink at it to make sure SOMETHING stuck

The Scott's bag was 3/4ths of the mix so that is mostly what is out there. It's looking pretty fricking gorgeous right now with the deep, dark greens. I'll probably overseed in the Spring again with just the Scott's since the ryegrass won't survive in the Jonathan Green's bag.

So if you weight the percentages by the bag size, it looks like this:

23% Endeavor II Tall Fescue
23% Faith Tall Fescue
23% Gazelle II Tall Fescue
8% Wendy Jean Creeping Red Fescue
8% Dakota Tall Fescue
6% Carmen Chewings Fescue
4% Eugene Creeping Red Fescue
3% Frontier Perennial Ryegrass
3% Stanton Perennial Ryegrass
3% Deepblue Kentucky Bluegrass

I thought the general consensus was wait at least 3 to 4 weeks before cutting TTTF, and cut at 3” for the first few cuts.

Don’t cut below 4”. When it’s mature stay at 3”.