There's no easy answer to this because it depends how much you are taking a day.
I've been on this plant for 5 years and I stick to 5-6g a day. The withdrawal is not very bad, just extreme fatigue, and it only lasts for a few days. Nothing will fix it though, not caffeine, not stimulants, only more kratom. I did this recently, and work retail, and they were some of the most exhausting days of my entire life.
When I was newer, I remember taking closer to 10-12g a day, running out (because I'd bought into that whole it's just like coffee thing) and experienced withdrawals that were probably about as bad as actual opiates. I'm still traumatized to this day by how bad it was, and it coincided with the loss of my grandfather. I was living in Hell.
I can confidently say anti-depressant withdrawal is a million times worse though.