In vosa’s book rules on driver’s hours and tachographs(gv262-02 revised 2009) it says dvla will ‘normaly’ turn round your aplication in five working days. it also says a driver must not normaly drive after 15 calender days or longer to be returned to base .so if its not normal for your sort of delay from dvla ,its not a normal circamstance.so carry on driving or dont return ur truck to base and carry on .hope this helps