Whether to replace the Predicta couplates (networks) pre-emptively is a tossup, in my view. If you build all of the replacements correctly, it won't do any harm. But you might be wasting your time and somewhat decreasing access to the PC board.
PRO:
Occasionally, a couplate does need replacement. Building a substitute is not rocket science; you can see how to do it in my Predicta articles or Bob's Holiday restoration thread.
Replacing them might increase the TV's long-term reliability, or at least your confidence in it. Replacing them might eliminate the need to pull the PC board in the future, a process that involves risk (risk of damaging the board or miswiring something).
CON:
Not all couplates go bad. If that were true, there wouldn't be a working Predicta left on Planet Earth. I suspect the majority of working Predictas still use their original couplates, or nearly all of them.
Tubular ceramic caps are extremely reliable. The resistors inside couplates may drift off value, but the question is, how much is too much?
Your replacement couplates will be bigger than the originals. Each new one decreases access to other components around it. This can complicate getting to test points on the board or even make it harder to replace a tube.
Each couplate has multiple terminals, and if you're too rough unsoldering and removing an old one, you may pull loose the foil on the board or otherwise damage it.
Replacing the couplates degrades the TV's originality.
SUM:
The decision requires you to judge the tradeoffs among several factors: originality, reliability, risk, and efficient use of the restorer's time.
Although I have replaced couplates myself, I don't want people to get the idea that automatically "shotgunning" all of them is a necessary part of every Predicta restoration. A more conservative approach would be to replace the high-risk caps and badly out-of-tolerance resistors on the board and then see how well the TV works.
Regards,
Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html