I rotate mine about every 6 months and have had NO problems in 6 yearsAt my dealership (can't speak for others) IF one of your keys stops working (AND the only reason is the car forgot it exists) we will do a reprogram for free (during the warranty period)?
The pain is you have to bring ALL the keys for that car in AND it takes about an hour?
I suggest to my clients that they rotate the keys about once a MONTH (that way if they forget and only do it once every three months it shouldn't be any issue)?
I know of 3 clients that have had the car forget that a particular key works. In each case, the owner put one key away (drawer, hook, etc) and only used one key and after 6-8 months they tried to use the "spare" key and it wouldn't work?