Which retainer option should I choose after Invisalign treatment?

Good morning all,My invisalign treatment is almost over (2 more trays to wear). However, I had a pretty bad experience with my orthodontist and don't trust her anymore. I read that after the treatment, 2-3 solutions for keeping the teeth straight exist:- Invisalign trays to change every 6 month/1 year,- Wire retainers My orthodontist wants to combine both solutions: Put a wire retainer  behind my teeth and make a dental mold with this wire to create a plastic retainer (not invisalign) that I would wear when sleeping. And everytime I would renew my plastic retainer, my orthodontist wants me to redo a dental mold for new plastic retainer (why not using the same mold everytime? she won't answer...). And it is a lot more expensive that the first 2 solutions I mentionned above. Do you think that my orthodontist's solution is reasonable or should I insist to have only the wire (or plastic retainer at night)? If I use the plastic one, is it really necessary to redo mold of my teeth every time I change the tray?