Has this issue really become a problem or question of timing? With one player? I've never known this game to have a problem before in this regard. However, I'm well aware that Daishain prefers a reasonably quick timely response, from players.
If I know that I cannot participate in a quick timely manner, in advance, I would inform him. If it were to be a lengthy delay, would then ask him to utilize the character as a NPC, if required.