This is a tricky question...It depends on several factors such as...
# of Relief Vets on the Gig platform in your geographical location (We are working hard to add new Relief Vets all the time!)
How much are you willing to pay? (Relief Vets value their time greatly so the pay needs to be attractive)
Timing! Most Relief Vets plan their schedules out weeks and months in advance. Gigs that are posted at the last minute are much more unlikely to get filled unless the pay is right and there just happens to be an available Relief Vet.