I went out to Meriphataud Mountains [S] and used Sublimation, then cast Dia on a Lizard. I let him beat on me. Sublimation kept ticking while I was taking damage. I took about 444 damage and then it said my store was full. I Cured myself to drop my MP down to about 350, used Sublimation, and I got 93MP back. It stopped because my HP dropped below the threshhold (as I wasn't curing myself).
For the next lizard, I put Regen II on myself to keep me from dropping too low. 631 damage from the lizard before Sublimation went to fully stored. Sublimation gave me the full amount of MP back, but it wasn't effected by the damage I took. By that, I mean, it took the time it normally takes for Sublimation to fill.