Particle effects are performance intensive in general. How big the impact actually is mostly depends on the device hardware and the complexity of the particles.
You can have a look at which properties affect the performance the most in the ParticleVPlay documentation. This component should also allow you to reduce the amount of code, as you only need this one component instead of the System, Emitter and ImageParticle.
We also noticed that performance can get better once a particle effect is loaded or used several times. I guess this is due to some internal performance improvements of the Qt particle system at runtime. Maybe gradually changing a particle property, like the lifeSpan in your example, can also limit the capabilities of these improvements.
I suggest you play around with the particle complexity until you reach a good balance between performance and looks.