RE: working age of Ni-Mh
Chances are good that they have deteriorated to much to be reliable. the only way to tell for sure is to make two tests. first charge them at 0.1C for 16 hours and the discharge them down to 0.9V/cell at 0.33C measuring the mahs you remove. If it is 80% of the rated capacity, they are probably good. If it passes the first test then recharge for 16 hours at 0.1C and leave them set unconnected to anything for at least 24 hours then do the discharge test again. If it approaches the same mah capacity as the first test gave, you have good batteries. The second test is to see if there is excessive self discharge which is often a problem as NiMh's age.