Board Thread:Naruto Discussions/@comment-25977287-20150704114842/@comment-5407586-20150704172105

Not once have I read that one can choose to gather different amounts of natural energy to enter Sage Mode. One just balances natural energy with one's physical and spiritual energy, and stop. Minato doesn't have as much chakra as other Sage Mode users, so it sounds right that his Sage Mode doesn't last as long as theirs.