WAN LLB Source-IP question

We have a SD-WAN with two wans and Source-IP LLB algo selected.

If I'm understanding things correctly, fortigate selects WAN1 or WAN2 randomly for each source IP and then all subsequent traffic from this source IP goes through this selected WAN.

My question is - when does this "route" reset or expire? What must happen for things to change so that source IP will go through other WAN that was used before?