Gizmo 
Having a smoke alarm battery start dying on you the same day a house down the road caught fire is slightly unnerving. Time to get replacement smoke alarms I think!
Just discovered as a result of this that Scotland now requires multiple smoke and heat alarms - with 10 year batteries and interlinking. Waaaay better than the English option which is "whatever £5 thing you can find with a 9v battery in"
szakib@gizmo Do have one per room. But there is no need to get new ones, just replace the batteries. :) If you are willing to spend time and money on them, there are also ones that connect to A/C and you never have to change batteries.
@szakib the actual detectors have a shelf life as well. The advice is to replace them every 10 years or so anyway and I would rather have a low internal battery to remind me than just forget. The ones we have at the moment are over 5 years old, so I’m not too concerned about upgrading them vs just swapping a new battery in. And I will probably add more in bedrooms when the kids are older but for now one on the landing should be fine - our bedroom doors are never closed so it is essentially all one space at the moment.