Multiple uses before dismantling?

If I use the cooker for breakfast is it ok to leave the mechanism attached and in the water to cook for dinner that night?

No problem at all unless the water has turned cloudy from a bag leak. This can happen but doesn’t happen often and less often with experience.

Yes, this should be fine. @RichardOL made a good point about water being cloudy - just take a look at it before you use it.