For standard internal residential doors a pair of hinges is adequate,  however fitting 3 hinges per door has its advantages. It will look aesthetically pleasing and from a practical viewpoint it helps spread the load evenly and will help to overcome twisting or warping. This can sometimes happen to doors over a period of time where heat and moisture are a factor.

One pack of self-adhesive intumescent hinge liners suitable for both FD30 and FD60 applications, unless otherwise stated. Successfully included within BS EN 1634-1:2014