AFAIK, SwapMagic is safe even to physically swap discs if you install a flip-top case (or in the case of the slims, blocking the sensors) as you're not physically forcing the drive to stop spinning or to open when it's not supposed to (since SwapMagic stops the disc from spinning). I used this method on a 75001 with no lasting ill effects before FMCB came out.
Chip-free/MC-free homebrew <3
FMCB 1.93 on MC for emergencies, NA
250GB HDD/FHDB 1.93/OPL 0.9.2 (GSM and non-GSM)/PS2 games, NO HDDOSD
80GB HDD/FHDB 1.93/POPStarter rev12/OPL644/GSM0.37/PS1 games, NO HDDOSD
SCPH-75001 (sitting idle, slims suck):
FMCB 1.92 on MC