when to get a free servicing done for my Grr 450

I bought my grr 450 ~1.5 years back. hardly drove it. odo reads ~6000 km.

already did 3 servicings. 1st at ~800 km then at 3000 then at 4500 (before a 700 km ride).

I got call from them today for 4th servicing, now should i do it? or just wait for few more months.

I think i wasted first 3 free servicings for no reason at all. my friend and i bought our bikes together his Himalayan it now clocking at 30k...