Hello. Can someone clarify this sentence for me?

"I, who must have drunk of it in my twice seven years' wanderings, am assured that it is worth while."

Does it mean that "I drank it twice over the course of 7 years?"

Or

"I drank it (once), during which I've been wondering around for 7 years and I drank it again (twice) when I wondered around for another 7 years?

Or

"I drank it a few times when I've been on two 7-year journeys"?

"my twice seven years' wanderings" = 14 years of wandering

It doesn't indicate how many times he/she "must have drunk of it" in those 14 years.

Thank you!