Is there a time limit when to change from boot disk to backup ?

[Tingles]

Neo2 installed with 16Mb Memory Card. Swapping to backups working OK, but I guess there is an issue of timing involved here.
From the moment I press START on the memory manager window and the screen asks me to load game and press X, how long do I have to eject the boot disK and load the backup disK ?
Cheers for any help on this,