I'd say that 3 years is a very poor lifespan for a fluoro ballast. I find plenty of old fluorescent fittings in this area which are 30+ years old and still on their original ballast.
Admittedly though, the modern ones don't seem to have the longevity of the old types.
You can check continuity with a regular ohmmeter, and use a megger to check for insulation faults. Testing for shorted turns requires more sophisticated equipment than that found in the average field electrical kit.
Agreed with the longevity issue on older ballasts. Took down some ancient 6' twin trough fittings last year in a big workshop; owner said they had been there since his grandfather owned the business. They were all working, bar a couple with lamp failures. JEEZ though...I could hardly lift the darn things!
There were thirty-odd of them, all replaced with more up to date affairs; HSE said the lux level was too low for a workshop. The present owner has said that their electric bills are down but more likely coz of the halide replacements and the management system.
If hindsight were foresight, we'd all be millionaires!
Hold on a second, guys! Just make sure that the tubes aren't of the 38mm RS (Quick-start) type. And the fittings that supply these tubes, contain PCB's, usually in the Ballasts. A fully sealed unit, but they have been known to leak Carcinogens(sp?)(Cancer-causing chemicals). Watch out!!.