My opinion:

If it's already running in there, leave it in.

Reason?

The solvents in Trans X (and many auto-trans additives) will soften and swell the seals to get the transmission internal seals to seal and hold proper pressure / shift properly. The transmission seals will set at this new dimension while you run it. If you replace the fluid with a fluid that does not cause the seals to swell as much as they currently are, you will likely have internal leaks = low pressures which will cause it to flare, to slip, to not shift at idle, and generally act impolitely when cold.

Once it's in there, leave it in there.

It's best to not change the chemistry dramatically if there isn't a good reason to do so.

__________________

Gone to the dark side

- Jeff