Retaining Coffee for 30 plus minutes?

I often get relaxed during CEs and allow 30+ minutes to pass before I go to the bathroom. Sometimes I have retained them for an hour or more. After around an hour most of the liquid seems to be absorbed.

The only problem I have noticed is after a while a lot of caffeine is in my system.
Is there any danger or downside to retaining them this long?
Are they more effective or is 15 minutes optimal? Tweet