Steps to switch account, assuming you have two or more memory cards. I have three for each PSN I use.
32GB:US + 32GB:JP + 8GB:SG
1. Sync trophies first.
- trophies are saved on the system itself, no sync = sayonara hard earned trophies after factory restoring Vita.
2. Restore the PSVita system, leave first memory card inside.
3. Deactivate system, don't format the memory card.
4. Vita restarts, enter Wifi info and 2nd PSN account info.
5. The intro video starts, now straight away swap out the memory card and insert second memory card. System prompt comes out, skip the video by rebooting.
You just killed two bird with one stone.
6. Once Vita done with rebuilding database for second memory card, activate account and enjoy.
Everything above can be done under 3 minutes.
Just like instant noodles.
Unless you only have one memory card, then you're forced to backup and restore each time. Making it 30 minutes per account switch.