How can this be alleviated? Don't hold it tight on full lock - use a tiny bit less than full lock. I don't know how the motor senses that assistance is required, but I imagine by turning the steering wheel fully and holding it hard against the end of its' travel, the motor thinks more assistance is required when of course, there is no further movement possible. So it burns out if continually repeated.

The same goes for conventional power steering systems.

I no longer have my Fiat,but the advice I was given was to avoid using the "City" function.This setting only serves to make an already light steering even lighter. Try to avoid holding the steering at full lock unecessarily and turning the steering wheel when the car is stationary. However,I do not think you need to worry too much about this aspect-my Fiat did well over 40k.with no problems of any sort . AFAIK these systems are fitted to many newer cars( not just Fiats) ,so must be reasonably reliable. You would be well advised to consult people on the Fiat Forum if you have any Fiat related problems or queries.