I currently finish Ashen Maw on day 32, which leaves me 48 days for DLC and bosses. This seems like more than enough time based on what other people have said in this thread? Could be wrong.
I only use Lethandrias to regen life while the fire blight is attacking me, but I don't know of anything else that would regenerate at the speed I need for the length of time I need. (I'd run out of potions pretty quickly trying to do this and rings of regen are too slow)
So the strat is : Spawn fire blight -> withdraw vela so the fire blight follows me away -> wait for fire blight to proc Shroud of Phantasm while healing with lethandria's AI script
If Lethandria's gets to "near broken", I have to be able to end combat (by killing the blight), repair, and then repeat the strategy after spawning another fire blight. I can't kill the fire blight without powerful summoned weapons (takes too long, i might die from not healing fast enough, or worse, I might spawn a second fire blight), which share a spell slot with withdraw. This means that without withdraw scrolls, or a weapon strong enough to kill the fire blight in 3 or 4 hits, I will not be able to withdraw Vela for a second pull.
Hopefully that all makes sense.
Edit: I should clarify that my script is set up to always end on a weapon set that doesn't have Lethandria's in it. This maximizes the lifetime of lethandrias by making it so that I'll almost never be hit while holding it. Even doing it manually I probably wouldn't have the skill/reflex needed to save lethandria's more effectively than this script does.