If you're talking about the player - I think nearly any time is ok - 'cept maybe after a loss or bad day at the office. Conversation should be about, 'What do I need to do to get better?' and 'What can I do to get more PT?'
And then the player should go do it. Or do his best to do it.
If, by some chance, you're talking about a parent - then almost never. (For me, I think it would be never…or lets say its never happened yet through 2 college playing sons).
The college season is VERY young - there will be plenty of lineup changes between now and end of season.