The longer the aquarist waits till he prunes the rattier the plant will look after trimming. Amano always advises to cut as soon as the plant reaches the surface.
I think that's a nice one since it avoids both too much shadow and the slowing of current .

Also, if you cut to the "bone" it'll take much longer for the plant to recover vs. having two or three inches left in place. Both of which again take much longer
to resume growth than simply replanting the tops (which makes a lot more work of course). So it's a balance not to trim too late and/or too far down.
For pickier plants it seems much better though to always replant the tops only.

If the plant is in bad shape for whatever reason or has stopped growing completely it's not a wise idea to trim at all. I'd rather wait until it starts growing
again meanwhile trying to fix the problem.

Have not been uprooting plants for years! If I swap over to another species I leave the old roots in place and plant right there. Never had a problem.
Well, did not try that with Echinodorus or big Crypt stands though.

Regards,
Detlef