How often should alkaline batteries be checked when they are in a device?
You don't need to check devices used frequently

Because you will soon notice that the device has gone inoperative, and will simply change the batteries at that point.  What gets 'ya is devices you rarely use.  

One option is to use rechargeable batteries in those rarely used devices, which is to say NiCd or NiMH batteries. They will still discharge, however they won't be damaged by doing so.  In fact,  NiCds and NiMH's normally self-discharge over time, so if left in a drawer for a year, they will be fully discharged within 90 days and spend 275 days in a fully discharged state, without taking any damage.  

Obviously after 90 days the device will not be usable and you'll have to take the batteries out and charge them; but you use them rarely anyway.  

If you need to have your rarely-used devices "ready and good to go", then my advice is to use primary cells (non-rechargeable), and change batteries annually.  Don't throw out the old batteries; just demote them to frequently used appliances.