I just had 2 lanyards.
One is attached to my centre D's and girthed to the tree loose so if I did slip it would cinch off and hold (I hope).
I often take 2 flip lines when doing palm TD's.
If I need to change over saws I often have a so called "shit rope" hanging from rear of my harness to use for saw swaps.
Why do I do that?
Coz I dont want to bomb crap on my lifeline, I dont want it hanging down the trunk of the palm where I might spike it, it's not wire cored, it's not as easy to do a change-over with it up in the head as not as heavy to flick etc.
Downside, you cant come to ground if you needed to. So I use a lifeline when cleaning palms but not for TD's, I'll come down with the palm when cutting blocks.
Debate/argument: If you needed to come back down on a cinched lifeline
(unless you had a figure 8 already) in you'd get stuck anyway. Plus, you shouldn't come down unless the palm is done anyway.
So, for palm TD's I take 2 flip lines. If I think for whatever reason I need to come down then I'll take a lifeline or "shit rope" to pull one up.