full
broad, wide
a broad span of interests

clear
The bridge has a clear span of 120 feet.

15-foot, 500-metre/500-meter, etc.
wing (usually wingspan)
The bird has a three-foot wingspan.

long
brief, short
ten-day, two-week, etc.
entire
allotted
The speech continued well beyond its allotted span.

natural (esp. BrE)
to prolong life beyond its natural span

time
life (usually lifespan)
The average lifespan of an American is 75 years.
the expected life span for boys born in the US

attention, concentration (esp. BrE), memory
He has a short attention span.
a limited attention span

cover
The book covers the entire span of Arab history.

over a/the span
Developments were monitored over a span of two years.

a span of time, a span of years