No need to keep a spare battery on hand. They do seem to last forever and they don't go all at once when they do go. The distance it works at will get shorter VERY slowly over time so you'll know and have plenty of time to replace it. Our 2001 Bug just had a new battery put in the fob about a month ago and I've never replaced one on any of the 15 or 16 Nissans I've owned...the last being an 05 Quest.
2011 Nissan Murano SL AWD in Glacier Pearl/Beige Leather
Dealer installed Remote Start
Nissan LED DRLs
Chromed stainless rear bumper protector
Retrofit 4300k HIDs
235/65-18 Pirelli Scorpion Verde All Seasons
iJDMtoy RED LED Bumper reflector lights