How long does it take to get back in shape?

Okay, today's question assumes that you've abandoned your martial-arts training for some time -- perhaps decades -- and are now wondering what you're in for as you begin training at 50, 60, 70, or older.  And it's a fair question, because many of us have to leave training while we juggle the usual components of adulthood: holding a job, raising children, mowing the lawn, and all the rest.
   Let's begin by defining what you mean by "in shape."  If you wonder whether you'll be as capable at 65 as you were at 25, the answer is no.  I've never met a serious martial artist who has gained speed, flexibility, and stamina in his or her 60s or 70s after laying off for long period.  So in all likelihood your goal should be to maximize the potential of your body as it is currently configured.  Losing weight if necessary and beginning a reasonable strength-training program can help, but don't expect your flying side kicks to take you above the clouds.  A "high kick" at 25 is generally quite different from a "high kick" at 65 or 70. 
    But, hey, does this really matter?  Even when you were younger, did you really need to put a side kick on the chin of a seven-footer?  No.  It was smarter to aim for the midsection -- a larger and less mobile target.  So if at your current age your side kick doesn't go higher than someone's midsection, what the big deal?  And note that we're talking for the moment only about the practical matter of self defense.  If your goal in resuming your martial-arts training is simply to get healthier, the height of your kicks doesn't really matter.  Again, your goal is to maximize your current potential.  Do as much as you can with what you've got.
   So let's answer the question: how long will it take to get into the best possible shape at your current age?  Answer: months, not weeks.  After, say, three or four months you should be able to ease your body back into  those old martial-arts moves as long as you don't rush the process.  Rushing the process will lead to injuries, and injuries could persuade you to quit for good.  If you're taking up your martial art after years of "vacation," you should speak with your physician.  He or she may decide that your fitness program should incorporate some physical therapy treatment BEFORE you injure yourself.  Trust me, a trained physical therapist can be a tremendous ally in your comeback program.
   If you don't rush the process and give yourself a chance, you will likely find that you've made substantial progress after 4-6 months and are well on your way to "my best shape for age X."  That's not a long time for something worthwhile, especially when we're only talking about an investment of perhaps an hour a day -- most of it spent stretching and working on whatever forms/poomsae/katas you remember.  And if you don't remember any of them -- a strong possibility -- just search online for your martial-art style.  Chances are you'll find tutorial videos for every style and every form, whether beginner or advanced.
   If you're a Senior in the Martial Arts, please share your advice on how to either stay in shape or get back into shape once you've passed 50.  Your photos and videos are most welcome if they can help inspire other seniors to get back on the martial-arts path.