long period of time.....
durante un periodo largo?
o
durante un largo periodo?
o
?da igual?
3 Answers
"durante mucho tiempo"
"por mucho tiempo"
" por una larga época"
" durante/por un largo rato.
You can add these to your list of possibilities.
I'm not sure if it's mandatory, but I usually see it as "período de tiempo":
durante un largo período de tiempo
I know what you are saying but to me it sounds a little too much 'word for word'. I'm not sure that this is the most natural way of saying it.
I would say: Durante mucho tiempo