Can we add 2 default route on checkpoint firewall pointing to two different ISP.

for example: ---> ISP A ---> ISP B

I am trying to do load balancing between 2 ISP through ISP redundancy ( weight 50% for both ISP)

But due to default route pointing to ISP A. All traffic leaves through ISP A and ISP B is never utilized. As i add another default route on firewall for ISP B with same cost, Traffic start leaving ISP B as well.

But after some time firewall removes ISP B route automatically. I want it to be in routing table always. Is this correct design?

I am doing hide NAT as well with 2 ISP external interface as well.