For me, it really depends on what era.
During MK9 I was playing from 4PM when I got home from school to 3AM when I went to bed then slept for 3 hours before I had to get up for school.
In IGAU, I didn’t practice or lab as much because I played Deathstroke who I loved from the beginning to the end. I just needed to get my combos down, adapt to patches & lab MUs. It was secondary game at the time too.
In MKX, I labbed a lot because I couldn’t find a character I liked & stay with until I settled with Mileena until I picked up Takeda & Scorpion (I didn’t lab with the latter at all). When I started playing Takeda, I suddenly loved the game & could play for hours.
I2, I didn’t play a lot cause I hated it after Deadshot was nerfed. I labbed a lot just to find a character I liked or find one to settle on after each DLC release (I liked Enchantress & Donatello) but it didn’t help, I still really didn’t like the game.
MK11 didn’t take much Jade wasn’t hard to learn or master just really really boring to play so I picked up Skarlet who was easy to master. Mechanics & certain bullshit made me drop the game: I still play it every so often, playing Sonya but it’s a hard game to play even with friends who actually like the game.