Second guessing our itinerary in Portugal

We are going to Portugal May 17-23 and second guessing our itinerary, would love advice!

Current plan:

Fly into Lisbon → train to Porto (3 nights) → train back to Lisbon (3 nights) → fly home from Lisbon.

But now I’m wondering if this is too much back-and-forth and if we’re losing time in transit. Would it be more relaxing / a better use of time to: Just fly into Porto and stay in that region the whole trip?

Or fly into Porto and out of Lisbon (one-way), so we don’t have to double back?

We want to maximize our time actually enjoying Portugal (food, wine, and wandering) vs sitting going back and forth. I am more of a relaxed traveler.

For those who’ve done it—what would you recommend? Is splitting time between Porto + Lisbon worth it, or better to slow it down and stick to one area? If we should stick to Porto, would love recommendations for the area. We are planning on visiting Douro Valley.

Any tips welcome 🙏