A question arose in our group about the retraining rules from Ultimate Campaign.
Retraining takes all your attention for 8 hours per day for a number of days based on what you're retraining. You can't perform any other strenuous activities while retraining, such as marching, adventuring, or crafting magic items. You can retrain only one thing at a time; you must complete or abandon a particular training goal before starting another one. Abandoning unfinished training means you lose all progress toward that training's goal and all costs associated with that training.
The question here is: what if you want to train twice in one day? Can you spend 16 hours in 2 consecutive sessions to decrease the number of days you have to spend training? It seems like the rules lean against allowing that, but there's nothing forbidding it either. The character in question also has a Ring of Sustenance, so he can rest between every session if that is relevant.