Big IP HA Setup - Long failover times

We have a Big IP F5 LTM/ASM HA pair set up in Azure, with multi-nic. The failover time is atrocious, at around 4-5 minutes, during which time our sites are inaccessible. Does anyone know of a way to speed this up? As far as I can tell it's not an issue with the actual F5 failover - that occurs instantly as you would expect, it's how long it takes for the F5 to interact via API with Azure to switch over IPs between F5 VE NICs. I would think there's a way to change the timer on when that API script kicks off, or manually kicking it off possibly.