I’ve always personally thought of “a few” as meaning generically “three or more” because you’d say “one” or “two” if less. If someone told me they’d pay me a few thousand dollars for my used car, then showed up with $1000 or $2000 I’d be surprised.
In the context of months I suppose personally speaking the range would be (this is not some official Purism statement here, so please don’t jump to conclusions) I’d reasonably conclude “a few months” to range from as little as 3 months to maybe as many as 9.