I see you are discussing DRO scales a little.
If you want to make them a permanent thing, totally forget the linear scales you are looking at.
I have been down that road for a few years now, and a few other people I know have been there as well. For something that you want to last a year or so, then fine, but any longer than that, they can become a nightmare. Just when you are half way thru a critical bit of machining and the damned things go wrong. A tiny bit of swarf, or any mention of fluids, plus the electrical joints and batteries are another weak point, will just cause them to pop their clogs.
Don't get me wrong, for a total beginner or someone who has got no cash to spare at all, it can be a way to go, but for long term operations you should be saving your hard earned pennies a little longer and go for a proper glass scale version, rather than going for this cheaper scale system and having to replace them a little down the line.
I still used one on my mill, for reading the quill, but that is only because I know that it will be safe up on the head away from the muck and grime, plus no cable movement at all. All other places on a mill and you are asking for trouble in the long run.
John