i actually dont recommend cutting it apart and sewing it back together yourself. the seams of any good binder are "flat" as opposed to seams you find e.g. on jeans to provide better comfort, since the material is not as soft as regular underwear and thus layered seams would most likely lead to chaffing.
When i wanted to have mine shortened at a tailor's they didnt even have a sewing machine to do the job.
I am currently owning 3 different binders which were all around 35 Euros...which is about the price of one or two proper bras i suppose...and I can say that now that i wear them in circles, wearing one for a week then retiring it for two weeks, my newer binders haven't worn out at all, as opposed to my first binder, which i was wearing whenever i was out of bed really.
So my guess would be that they last longer when they're left alone for a while after washing them.