couple-
noun: couple; plural noun: couples
1.
two individuals of the same sort considered together.
"a couple of girls were playing marbles"
synonyms: pair, duo, twosome, two; More
informal
an indefinite small number.
"he hoped she'd be better in a couple of days"
synonyms: some, a few, a handful of, one or two
"I have a couple of things to do"
That is what google says about the term "couple".
To me, when someone says a "couple" years, it means at least 2 years. Not an exact time but a small amount.