Do we need to make lodging reservations in advance?

In April and May, I expect you can find places to stay, but should expect the most popular and most centrally-located lodging, especially smaller hotels and inns, to be fully booked.

At minimum u should reserve in adv your first few nights and last few nights.
And especially Lisbon.

The first time I traveled around Europe, and for a number of trips after that first adventure, booking hotels was a matter of going to the local TI office where they maintained a list of hotels and rooms to rent. It was easy, and because the staff at the TI spoke English and would call the local hotel to get the room for me, it was a pretty easy and reliable way to arrive in a strange city knowing that you could find a place to rest your head.

For a time after that, I found that it gave me peace of mind to book a room by mail. This stifled spontaneity, but it was a comfort knowing I would not be sleeping in railroad waiting rooms.

Now, however, emails are the way to go, and while you are looking for the TI to assist you in finding a room, I am emailing the hotel directly from many miles away, and have probably booked the room before you thought about which city you are in. You will have more intense adventures than I, but I may sleep in better rooms and inns than you. It's a toss up.

If you are not too particular on how nice the place is or if money is not a prime concern, then you can travel 'spontaneously'.

I travel the way you are proposing most of the time, but how many days in advance I make my internet bookings has been creeping upward over the last 3 years. I travel between May and mid-September, and I've fairly often found no well-located rooms remaining in my (budget) price range. A good part of the problem is that I often need air-comditioning, which limits my choice of hotels. That will not be a problem for you.

One thing you need to do in advance is check on holidays and special events at your destinations. Those can really reduce room availability and drive up prices sharply.

Thank you all for your replies. Based on what you said if it is really important to be in a particular place, we'll book well in advance. It also looks like booking only 24 hours ahead may be problematic, so we'll try to get better at figuring out where we'll be two to three days in advance. The small decrease in flexibility will be worth it to make sure we have a nice room. Thanks for your advice. Keep on traveling.

My wife and I are going to Portugal in May 2019 for 3 weeks staying in Lisbon, Obidos, Aveiro, Braga and Evora. I just finished booking the last hotel/apartment yesterday. I use Booking.com to find suitable properties with desired amenities and then use Trip Advisor reviews to confirm suitability and then make a reservation that I can cancel on Booking.com. I have used that process every year for the past 10 years and it works well. Many good places are already fully booked so it is wise to make reservations early.

After a vacation of no reservations (other than first and last nights) I feel like I can do anything! I absolutely love, love that feeling. I've stepped out of my comfort zone and had a great time, been extremely flexible, had adventures discover me. That being said, my husband won't do it...I see a look of panic on his face when I even talk about it. We did it partially in the Netherlands a few years back, and while it worked out fine, he's just not interested. He likes to be set when we get on the plane. Consequently, I haven't winged it for a few years. You need to decide with which you and your travel companion(s) feel comfortable. If you are both/all onboard and you are both very flexible, I'd say go for it.

Portugal is experiencing a tourism boom. (Maybe the rest of Europe is too.) I visited Portugal for the first time this May. I couldn't get over how touristy and crowded both Porto and especially Lisbon were. Booking lodgings in Lisbon a few weeks out (I rarely book things much further out), there were slim pickings at good prices by then. But if you aren't particular about price, you can probably get away with last-minute booking - and some towns are less booked up than others. It wouldn't hurt to book a few places on say Booking.com with free cancellation til near arrival and change them if you change your plans.

Hi William
We have traveled in Portugal during the same time frame ( late April, early May) twice over the last few years. We have always booked our initial stop ( Lisbon both times) and last time we also booked Porto.

For the most part we had no trouble with either arriving in a town and finding a place ( either with Rick Steve's book recommendations, or having picked a couple of potentials before hand) Or booking on-line the day before. However, April 25 and May 1 are both holidays there. On our last trip these fell either on or close to a weekend and we did struggle a bit to find a place, for one of the nights. So I would suggest checking when these fall and watching those days on-line to see if they are booking up.

In general my own finding is for bigger cities the cost savings from booking ahead outweigh the flexibility, and this was one reason we booked Porto.