I had an 08 spot and greased it about every 4 weeks unless it was a very bad winter ride,then i would grease it every 2 weeks.
This was probably overkill but it kept it very smooth.I would do about 30-50 off road miles per week,every week all year round.
I had to remove one of the shock bolts to allow the swing-arm to move so i could get a grease gun onto the Zerk.
Just remember to clean the zerk with a rag before greasing so you dont push grit into it when greaseing.And it dosent need much grease,i would push grease in it until the grease gun went very stiff and you couldnt push it easily.