My reading of the regs is that you were (are?) allowed to use it to land in an alternate airfield (it's primary purpose) and that airfield may be some distance past your destination in you line of flight, either side of your destination, or having been overflown (turning back). (going way back when I did FRP and NavEx preparations)
IIRC you are not allowed to use it to land at your destination unless there is bonefide verifiable reasons why you could not land earlier (precautionary), or that conditions on arrival had demonstrably changed, delaying your touchdown (ie, showers/heavy rain, held in circuit due to traffic, strip temporarily closed due to other reasons).
45 min is about 16kg of fuel for most people here with Rotax/Jab engines, not much really....