I just went through my OM and found that the recommended time before disconnecting or reconnecting the chassis battery main switch cable is "two minutes" with the key in position 0 (zero), which is the off/lock steering wheel position. I had always thought it was "ten minutes".
Obviously, better to take too long, than too short a time.
2018 (2017 Sprinter Cab Chassis) Navion24V + 2016 Wrangler JKU (sold @ ????)
2016 Sunstar 26HE, V10, 3V, 6 Speed (sold @ 4600 miles)
2002 Roadtrek C190P (sold @ 315,000kms)