No one is suggesting people not take the Medicare benefits that we have all earned. The point I am making is we can't just declare Medicare for all without looking at the Plan and how it is funded. Right now your Medicare benefit is being partially paid for by people who are not entitled to receive any benefit, just like you and your wife paid into Medicare for all of those years to pay for everyone else's benefits. 
In  2015 there were 55.5 million Medicare Beneficiaries 
http://www.ncpssm.org/Medicare/MedicareFastFacts

In 2015 the revenue outlay for those Medicare Beneficiaries for those 55.5 million individuals was 646 billion dollars. How much do you think it will cost to insure the 330 million individuals currently living in the US. 
https://www.cms.gov/research-statistics-data-and-systems/statistics-trends-and-reports/nationalhealthexpenddata/nhe-fact-sheet.html

I will let you do the math. Remember our entire federal budget is around 4 trillion dollars.