A timescale of grief depends on the person who is grieving, whom they're grieving for and the circumstances.
When my Nan died of cancer, despite being someone I loved with all my heart, I didn't grieve all that long. Aside from the fact that I was grieving for the loss of my relationship concurrently, I was relieved to see her suffering end.
When my brother ended his own life at the age of 24, it took me a long time to get my head around it. Years!
Denise Fergus... How the bejesus does that woman cope after what those two inhuman savages did to her innocent little child? I'd have lost the will to live if I were her.
Grief is very individual.