OK when it comes to gang members you just can't wake up one day and say "Hey I'm retired from the life that's it. See you later."

There are rules.

So I see these guys retiring from the mob on the other hand and it seems like if you decide that you want to retire you can just walk away at any moment.

Why is this allowed? Especially if you are still active and making a profit for them? I would think a boss would have to approve this decision yes?

It’s a well kept secret — but word is that the Mafia has what's called the RRP, which is an abbreviation for the "Racketeer Retirement Program" — a nice little severance package provided to those hoodlums who have reached 30 years with the company, or "Brotherhood."

Each eligible mafiosi receives a 14-Karat Gold Meatball trophy, as well as one quart of homemade marinara sauce and one pound of freshly made mozzarella, each month, for the rest of their lives.

Made members retire when they die, are old to where they cannot perform their duties or a medical emergency has limited their physical capacity is some why that they can not perform their duties.
Associates can retire more easily, unless they know a lot more than they should or are way valuable.
Hangarounds can retire anytime.

When they get old they just retire, most likely it is gradual. Even when retired they would still be expected to come in if called, but it's more practical to think they just have to keep up occasional contact, or be reachable, No boss is going to make a member keep at it, except in Soprano-land,