Unfortunately that only works if the new TRE are exactly the same length as the originals and if the threaded portion is the same in terms of blind thread etc. I have done that before as a 'get me going' but as the TRE also wear which is why you are replacing them, successive tracking adjustments over the years may have moved the original set point. And of course who's to say that your tracking was right to start with. Poor tracking doesn't always show up. It can be straight and even, but still wrong.
But like I say, it's a pretty near enough measure usually. If you are happy with that then you can return the new TRE to the original set point then wind one on and one off in equal turns to move you wheel but keep your tracking.
Me? I like the £35 option.
Chris