In ,
RickH wrote in part:

I have replaced quite a few of the older ones which did not last more
than a year. My newer ones are still going after 2 years. I had to
return some recently to HD because the entire tube did not get
energized, (only the top half of the spiral was glowing). The guy at
the store gave me a fight over returning 6 bulbs all of which I
claimed were defective, eventually he caved but probably never
believed me.

Only half the spiral tubing glowing?

I have seen a few look somewhat like that - about half the spiral
glowing much more dimly than the other half. That problem does fix itself
after a minute or two of warmup.

The first time a CFL is used after it is put in place, it may take
several minutes - but it usually takes just 1 or 2 minutes.

- Don Klipstein )