Long struggle, followed by a lucrative franchise of gradually

Which authors do you know of that had a long, relatively unsuccessful
career and then, upon a breakthrough, comfortably settled into writing
the same really famous characters & books over and over for years?
Extra points if the books in question dropped in quality over time and
if there is no compelling plot reason for a sequel.

Examples:

Laurell K. Hamilton

I read the first 4 or 5 Anita Blakes and I thought she was really
milking the series after the first 2 or 3.  Recently I saw an advert
for a totally unknown book from her, in the back pages of a second
hand book that was at least 15 yrs old.  Something like "get those
other DAW bestsellers for $1.50 +  0.25 postage."

Which kinda got me to empathize with her - she paid her dues, nobody
cared, now she's famous without doing much work.


Chelsea Quinn Yarbro.

Yes, St. Germain.  No, it's only a coincidence that it is another
vampire series.  Or maybe not, there is an audience for romantic
vampire stories.  She wrote good, grim stories for years, but never
had a big hit, I think till St. Germain.  Since then - St. Germain ad
infinitum.


GRRM - Not so famous, till Ice and Fire, which he is now speed-writing
on the assembly line.  Sarcasm - I couldn't resist.  Where he is
milking it a bit is by re-issuing all of his, excellent, past work.
He hasn't shown much decline either - Feast wasn't up to the preceding
level, but it was still quite acceptable.