Continue refinement until the end of 5 year warranty?

I did 2.5 years of Invisalign active treatment and 1 year of refinement (so 3.5 years since start). M my dentist told me that for a small fee (350 dollars?) he can do one more round of scan and get me more trays to last until the end of 5 years. I kind of just want to finish the treatment soon so I'm leaning toward just get the Vivera retainer. But it seems like a good deal to get more trays for just a bit of money. is it recommended to keep on getting refinements until the end of 5 year period?