You have a few option for this depending on how faded they are.
So if very badly faded, ideally you would want to introduce some colour to the trim in which case you have Solution Finish and another perhaps less known one called Feynlab Plastic Black. Both contain effectively black 'dye' type ingredient so will recolour the trim back to original. The feynlab will outlast solution finish but is more expensive per ml. So approx 6 months from solution finish, Feynlab would be 12+ months.
For lightly discoloured, you have a few more options. So solution finish again, Feynlab Plastic, Gtechniq C4 and TAC System Quartz Magic (there are others). Again the ceramic option are the more durable however they again are more expensive per ml of product. Solution finish on lightly discolour will last a good while and I always recommend to do a couple of coats and top up after a month or so which overall will give it better durability and 9+ months is easily achievable.
Further to this, general dressings, like Carpro Pear, Tac Systems Seal and others, can be used intermittently to again prolong any of the above.
A bit long winded, but hopefully will help