I don't know whether M. Delcamp will see your message as he doesn't routinely read all posts here, English not being his native language. However, since he says that the times he suggests are the minimum necessary, it's probably fair to say that you could put in a little more time if you are able. But remember to have a break at regular intervals, keep your arms and hands relaxed, and don't practise so hard or so long that you are feeling undue strain, as this can lead to damage. It's best to build up gradually.
Classical Guitar Forum.
"Experience is something you don't get until just after you need it." - Steven Wright