That is not the full truth.
When you leave JAAland, you will loose your validity, latest when your last check ride and your last medical runs out. On your JAA license, you have a date, when you don't come back withing that time, your JAA license will run out. You might have to retake the examns, depending on how long you were away and what you did.
I was 3 years out of JAAland. My JAA license was valid for about 10 years, so no problem. All my check rides and medical became invalid. As soon as you come back to a JAA operator, you have to do a check ride, a medical or a new type rating, if your old type rating was expired. Depends on your country and how they handle it. After that it's fine. You get a shiny new JAA license.
If you haven't left your old JAA operator, then it's even easier. Just do another LPC and a medical. A JAA LPC has to be done on a JAA sim/aircraft and with a JAA TRE.
Before you leave, please give your country's civil aviation authority a phone call and ask them exactly what you have to do to keep your JAA valid. Then act accordingly. It's a good thing to get the answer in a written form.
Good luck and enjoy the experience outside!
Dani