Advice is for the first 6 months but I'll be honest my son is currently in our room with the monitor on and he's 8 weeks. With my daughter I was upstairs with her until she was 12 weeks
My first was in his own cot/room at 4m. My second at 6m. My 3rd is 4wks old and spends some of her naps in her bassinet in a seperate room at times. Monitors were/are always used. I’d make sure the sound was up, kept the monitor on me or if I was say washing dishes in front of me and then would periodically physically check them.
Minimum of 6 months before sleeping in a different room, it’s to do with your breathing regulating theirs. SIDS is more common when baby left in a room sleeping alone, I personally wouldn’t risk just using a monitor until over 6 months x x
I put my 2 month old down for naps in the bedroom and have the monitor close to me & go in to check on him every so often. Works for us.
The NHS recommends that baby sleeps in the same room that you are in until a minimum of 6 months old. So naps and at nighttime.