For any tropical, I'd repot immediately (at any time of year), cutting back any bad, smelly roots. As far as the maple goes - how sure are you that rot is the problem (watered too often?)? And the pine should also be done if you think it's in danger of dying, because what have you got to lose? What kind of pine is it, and where does it live, in what kind of soil mix?

As I said, I have no answer to those questions as this isn't about a real situation, it's a general question! :)
Suppose that we're sure that the problem is root rotting. So in your opinion, repot immediately tropicals and pines, right? And perennials?

If anything is rotting (and you know that's the problem) of course it needs to be taken care of - seasons no longer matter if it's 'life and death'.

The problem with root rot is an immediate situation like lung cancer or colon cancer. If you catch it early enough the tree can be saved. However if you wait till the "Proper Time" the damage may be so severe that it is beyond redemption. Root rot and its subsequent cures are always ranked in the desperation category; you might lose the tree for trying to fix it, but you will surly lose the tree if you don't.

how can u tell if your tree has root rot ?

Neda if you suspect yours does, what are the symptoms? Each situation will look a bit different depending on the tree, the circumstances, etc. and many of the symptoms can look like something else besides rot.

First sign or indication; the tree stops needing water and the soil stays wet. Leaves and or needles start to turn a buttery yellow. At this point if you have ruled out pests or natural cycle of a particular tree it is a good idea to remove the tree from the pot and inspect the root system. Rotted or rotting roots look brown and are often mushy---they smell bad as well. Lack of new white roots that look like Chines noodles may also be an indication of root rot.

lucy and vancewood,
many thanks for the advice :) It may be surprising to you, but that was a question to which I have never been able to get a straight answer :)

Best regards
FP

You will find that many who have had a run in with root rot only find out after the tree has died.