Glacier NP and Yellowstone NP - how long to visit

Unless you're an avid hiker, Yellowstone is good for 3 days. One day for the north loop of the figure 8 road system, one day for the south loop and one day out to West Yellowstone and back. So, 4 nights and 3 days. There's enough time to get in a few short hikes each day. I like to stay in Canyon Village on the east side of the figure 8 center. It has several shops, a ranger facility and multiple places to eat. I wouldn't go to the trouble of moving my rig daily.
Glacier is basically 2 nights and 1 day. Really just one road through the park to cruise. Both times depend on your preferences for lollygagging and hiking. I'm a pretty efficient traveler.

The answer is determined by what you want to do. We don't hike to the furthest spots in the parks. Our motto is, "If we can't drive to it, we won't go". Not the best way to enjoy a national park but it suits our ages and abilities. So we spent two days in the Grand Tetons, two in Yellowstone and two in Glacier. If you hike, you're going to need a lot more time than we did. To make up for our lack of physical ability we always see the welcome center and the movie first. The final thing we do is buy a professionally published book about the park with lots of pictures of things we didn't see. Works for us; certainly won't work for all.

Parrothead Mike wrote:
Here's a suggestion you might not expect, drive through Yellowstone and head south to Grand Teton National Park and spend a 3-5 days there. Just my preference. It's definitely your choice. :)

Strange 99.9% of the people like Yellowstone better

We spent 5 days in Yellowstone and 3 in Grand Teton and would not cut any shorter than that.

Parrothead Mike wrote:
Here's a suggestion you might not expect, drive through Yellowstone and head south to Grand Teton National Park and spend a 3-5 days there. Just my preference. It's definitely your choice. :)

X2

DW and I got home from last Friday our most recent trip to Yellowstone and Grand Teton. We spent the first two weeks of June in Yellowstone and the rest of the month in Grand Teton. There were still things we wanted to do, but it was getting way too busy for us.

As much as you can! Retired, which means you have the all-access pass? So you're not limited to the 7 days like us youngsters. My preference is Glacier far and away. Many different areas in the park to explore and hike. We could/have spent a week there and it's not enough.

Definitely preference, and agreed that hiking will mean you need more time, especially in Glacier.

I'd allow a minimum of 4 full days in Yellowstone, one of which should be spent visiting Grand Teton National Park, just to the south. I'd suggest 5, and add the Beartooth Highway (northeast entrance of the park) - it would be a dandy on a motorcycle! However, for that, you'd need to be sure to be there between mid-July and early September, or the road could close due to snow. If you need hookups, you will need to camp at Fishing Bridge, or outside the park (West Yellowstone being the best option for that, with several decent choices of CGs with hookups). If you can go for 5 days with no hookups, then almost any of the other reservable campgrounds inside the park will work for you, assuming your rig will fit in the site. Campgrounds in Yellowstone are older and many sites won't accommodate much bigger than about 25-28' total rig length.

In no case would I ever recommend spending just one day in Yellowstone. :)

Can't comment in detail on Glacier, as we have not yet been there. Going later this summer, if plans hold.

Here's a suggestion you might not expect, drive through Yellowstone and head south to Grand Teton National Park and spend a 3-5 days there. Just my preference. It's definitely your choice. :)

Depends on you
Honestly
If you are "Car touring" and not planning on doing any hiking/looking one day in Glacier and two in Yellowstone.
If you are spending time looking, hiking, taking your time three or more days for Glacier and a week in Yellowstone.