...what a topic:
I am almost 44, I've been battling this thing for the last 22 years,...and no I'm not kidding you!!
I got to say this; I surely believe there is all sorts of different reasons in how to develope patella tendonitits. And therefore the approach to get rid of this might vary a bit. In my case...my legs are "very strong",...so there is no need for me to strengthen my quads.
I think you can fully recover,...but you gotta be aware that this thing can and will come back...you gotta fins out what your weakness is that causes this problem!!!!
For me it's all about hip flexibility. If the hip fexors don't do their job well it forces so much more work on to the patella tendon and makes me run tight with to much of a forward lean. I'm always especially proned of getting this injury when I get into the last few weeks of sharpening for shorter races (mile to 5000).
I don't think laying off helps much, it could take month if not years to "just go away". And I've been there too. You need to stretch your hamstrings, quads and hip flexors and work on "core strength". The more upper body strength you have, the better will be your running style and it will take pressure away from the knees.
If you run while hurt, try to start easy and stop after a mile and stretch, run your "filler mileage" very slow. Try to run more from the heel...like a marathoner. Don't make the mistake on running in shoes that are "too soft" though it sound like a good idea, it will make the problem worse. Stay away from uneven surfaces and make sure you change shoes frequently and that make sure that your runnung form is proper with "no knee wabbling action". Shoes need to be flexible but with a bit of a posting, "don't wear heavy control" shoes or full length "stiff inserts".
Even if you won't fully recover this does not need to be something that ends you're running career...it might save it...because when ever you're overdoing something your special friends below your knees will tell you to slow down and reinforce "core strength", "easy miles", "yoga", "ice" (3 times a day)and ibuproven (at times)...
I've ran around 3000 miles last year and the year before with almost no problems but there where occational flare ups.., but I also had masters PR's from the mile to the marathon!!
Stay positive!!