Speaking from personal experience or opinion?
I was at their service centre recently to check my Miband which was not synchronizing to my phone. The few customers before me either have problems with motherboard or audiojacks hardware issues. Without warranty, the cso told them its not that worth to repair because its more cost effective to get a new one which will come with a new 1 year warranty. So you can say its more like experience and opinion. I do agree, especially for Redmi series which are mostly on the lower price range.
I remember 2years ago my HTC phone needed to change a new motherboard, and I was quoted $230. The cso also tell me don't bother because its not worth at all for an old model which after repair only give me 1 month warranty only