You are worried about your JAA licence while away flying in Africa and what will happen to your JAA licence without renewals?
OR
are you flying in Africa on a African licence issued and valid on the basis of your JAA one(?) and therefore require the JAA licence to be valid at the same time?
If it is the first one, you can let it all lapse and then renew it all when you get back.
You don't have to do a medical initial issue again, just a normal medical gets it back to speed again.
If you have a frozen atpl, then yes, if you have not revalidated your IR in 7yrs you can lose your subjects, however there is a clause that if you have held a ICAO IR and used it elsewhere in that time, then the clock ticking does not apply. However after 5yrs from doing your last IR you must do a revalidation IR exam with a CAA examiner. Doing the IR will cover your BFR and plane type used for the test in one hit.
As for going beyond the period of the 5-10yr licence, best to check on the CAA on that one. Again, maybe just a simple matter of paying the fee along with your flight test results.