The phrase "across a span" is correct and usable in written English.
It can be used to describe something that occurs or exists over a certain distance or period of time.
Example: "The project was completed across a span of six months, showcasing the team's dedication and hard work."
Alternatives: "over a range" or "throughout a period".
The stories in the book will have been written across a span of fifteen years or so.
So Mr. Trump seemed to be settling in for a dialogue that could take place across a span of meetings.
Journeys will examine works written across a span of some 2,300 years, from Chinese philosophy to American short stories.
As she survives the night in the field, her thoughts wander across a span of memories that are the accumulation of a lifetime.
When Sid Caesar watched himself on "Your Show of Shows" with me that afternoon, he gazed across a span of fifty-five years.
Enter the Australian actor Hugh Jackman, who gallops into Meg Ryan's life across a span of more than 100 years in the frothy romantic comedy "Kate and Leopold".
Across a bridge spanning the Tigris River, in the mostly Shiite neighborhood of Kadhimiya, several Iraqis at the bazaar in front of the main shrine echoed some of that optimism.
I cannot think of another GTA release that's had so many releases across so many different platforms across such a span of time.
There is no secure cultural affinity between ancient pagans and modern ones, and the language game issue promoted by Wittgenstein holds: entering someone else's world view, especially across such a span of time is next to impossible.
In the interim, though, we do have the real-world evidence of Blue Zone populations about diet, lifestyle, and health across just such a span.
This strategy points up thematic and stylistic links across a wide span, which is historically useful.
