That's a little too absolute. For the past 15-20 years, every time I seem to have some accepted pattern among the schools, something else comes up. What I would say that 5 years beyond your initial degree or other prereq mechanism, schools want to see some evidence of recent academic work in the sciences. That does not mean a full post-bacc or masters. However, that is by no means a hard and fast rule across schools. There are some that still say 10 years and most say nothing on the topic other than a vague recent work or academic ability. This is even muddled as schools are moving from specific prereqs to core competencies and thus the issue becomes even more diffuse. As one of favorite lines from Month Python says "Its all rather confusing really."