Many new electronic ballasts now have end of life detection for the bulb and for the ballast.

As bulbs reach the end of their life more current is required to light the bulb. This generates more and more heat at the electrodes and can eventually crack the glass. (you've probably seen this in high output bulbs in old freezers with magnetic ballasts). The higher intensity of the bulb (HO or t5) the greater the possibility of a catastrophic failure.

Electronic ballasts will shut down when they detect the bulb is reaching the end of its life. when the EOL circuit activates you will get intermittent operation and the bulb will go from working fine to not working and back again.

Always try a new bulb first. If that doesn't work check that the connections are good and if they look fine replace the ballast.

Electronic ballasts have a lot of capacitors inside and when these capacitors fail you get intermittent starting or no starting. Just like a compressor