The phrase "a series of extensions" is correct and usable in written English.
It can be used when referring to multiple additions or modifications to something, such as software, contracts, or physical structures.
Example: "The software update included a series of extensions that enhanced its functionality and user experience."
Alternatives: "a set of extensions" or "a collection of extensions."
What I wouldn't like is a rolling cliff edge whereby there are a series of extensions.
Vornado's exclusive right to build the tower expired in August, after a series of extensions dating to 2007.
Architectural plans showed that a series of extensions had been made after the home had been built six years ago, possibly to accommodate more of the family.
He was granted a series of extensions, and delivered several provisional cuts of the movie, including one, in the summer of 2008, that was within the desired limit.
The American lawyers arranged a series of extensions, the last of which expired in February of this year, according to lawyers for the American victims.
Mr. Lyons negotiated with the new owners, Zar Property NY, for a series of extensions before the market rate took hold.
He liked to tell clients that he'd kept his store going well beyond its natural life span by putting all the lamps on a series of extension cords and plugging the last one into an outlet at City Hall.
After a series of extension, ligation, and cleanup reactions, the DNA was labeled with a fluorescent dye.
Second, even if animal minds are massively modular, and even if single incremental extensions of the animal mind preserve that feature, it's quite possible that a series of such extensions of animal minds might have led to its loss.
Then a series of arm extensions, to make sure the microphones were properly aimed at their target.
Instead of passing a replacement, as might happen anywhere else, Congress has approved a series of brief extensions of the old law nine of them, to be exact.
