Dresden Museums--How Much Time to Visit?

The Historic Green Vault will take at least an hour, much longer if you want to see the larger New Green Vault collection as well. The Old Masters Gallery will take an hour or two.

We are also planning a 2 night stay in Dresden and then heading to Berlin, the end of June, and I would love to visit the Saxon Switzerland National Park. Where are you planning on going and what will you be doing? It looks like it would be fun to take the boat there.

How long the museums take depends on your interest. The Old Masters took almost two hours in my case, and I'm not interested in paintings. Also keep in mind that Berlin has a great (and underrated) gallery, the Gemäldegalerie. There are two Green Vaults, historic and new. The Historic Green Vault took me one hour, the new one 90 minutes. The armory includes the Turkish Chamber, which I found very interesting. I think I spent 90+ minutes there. Both have no equivalent in Berlin.
Usually it's recommended to see one museum in the morning and one in the afternoon, and visit the (small) old town (+ restaurant) between the two museum. So, with just a late afternoon I guess only one museum + the old town (Zwinger, Frauenkirche, Brühls terrace, Neumarkt) is possible.

We spent a week in Dresden this past October , and it wasn't enough , particularly as we are lovers of Art and Architecture . When you visit the New Green Vault ( upstairs ), allow adequate time for the collection of work by Johann Melchior Dinglinger , one of Europe's greatest goldsmiths . The detail in his work is staggering , this work is unique - https://en.wikipedia.org/wiki/Aurangzeb#/media/File:Hofstaat_zu_Delhi_am_Geburtstag_des_Gro%C3%9Fmoguls01.jpg . Also if you have a bit of time , jump on the # 11 tram and go across the river to Neustadt to see Molkerei Pfund , a dairy shop with exquisite Majolika Tilework bedecking the whole place . - https://www.google.com/maps/place/Dresdner+Molkerei+Gebr%C3%BCder+pounds+GmbH/@51.0623968,13.7574637,16.54z/data=!4m5!3m4!1s0x4709cf39c6449083:0xc4f529c863f6b45a!8m2!3d51.0638235!4d13.7596451

I actually have my heart set on Saxon Switzerland National Park myself, that's what makes the museum planning so challenging. I would hang on in Dresden the day we head to Berlin and see more museums, but this park is really calling to me. I was thinking take the train there and the boat back or the other way around. (One way is much faster on the boat). My rationale is this is a very city-heavy trip and the back end in Dresden and Berlin is also very museum heavy. So with limited time it seems like a reasonable call to forego some museums for time in the outdoors, weather permitting. I also would like to stop in Bautzen on the way from Goerlitz, but that would take even more time from Dresden so I may opt not to. The more I research it, this area of Germany really has even more to offer than I realized.

I hope you left some time for Gorlitz , it's magical . We spent four days there after Dresden on our way to Prague . Magnificent Architecture of many styles . As you probably are aware , Gorlitz was the principal filming location for " Grand Budapest Hotel " Some shots were done in Dresden , and the dairy shop , Molkerei Pfund stood in for the fictional patisserie " Mendl's " . While Mendl's doesn't exist , it's a not so subtle nod to Demel's , in Vienna

Yes, we are spending two nights in Goerlitz. We will arrive on the late side the first day, but will have a full day in the town.

We are also planning a 2 night stay in Dresden and then heading to
Berlin, the end of June, and I would love to visit the Saxon
Switzerland National Park. Where are you planning on going and what
will you be doing? It looks like it would be fun to take the boat
there.

Realistically, as a day tripper without a map, you can see only two things in Saxon Switzerland: the Bastei or Königstein fortress. For everything else you need a map.
It's possible to see the Bastei and take the paddle steamer from and to Dresden. But the Bastei is a very popular site, so I would recommend to take the S1 to Rathen (takes 30 min), cross the river on the little ferry, hike into the Amselgrund, through the Schwedenlöcher up to the Bastei, and from there back to Rathen. And from there you return by boat to Dresden.

Yes, we are spending two nights in Goerlitz. We will arrive on the
late side the first day, but will have a full day in the town.

In case you haven't already booked: Frenzelhof is highly recommended. A Late Gothic merchants home with a private chapel and just six rooms or so.

We were just in Berlin, Gorlitz, Dresden in August. Really liked this area and plan to go back next Spring to see things more in depth.

For Dresden, know you asked about museums, and we didn't do too much this way, besides strolling through the Zwinger complex (we didn't give this city enough time). But if you have time and need a break from museums, etc. we really enjoyed renting bikes and riding out along the Elbe to the Blue Wonder bridge. Relaxing, pretty ride along the river, if you have a nice day. 4 miles to the bridge and then you can eat at the Schiller biergarten under one end of the bridge. (Can also get here by tram.) Their Zwickel beer from Feldschlosschen is the best beer we had in Germany. Scenic spot, great food, and perfect for a nice evening excursion.

Gorlitz was great, very charming and walkable in the historic Old Town. Stayed in the Untermarkt at Hotel Borse. Was perfect. Close to the river with its outdoor cafes on the Polish side. Also, one of our best meals of the trip was at the restaurant Patrizierhaus St. Jonathan. Fancier place but incredible food. Their Silesian Heaven dish was really good.

Scott