Bernese Oberland Regional Train Pass

The Half-Fare Card for visitors is good for 30 days, so it will cover 2 consecutive ten-day Berner Oberland passes, as long as they fit within the 30-day period.

No reason you cannot, although the Tourist Half Fare Card is only good for 30 days and you are there for 35 days. You could get an annual Half Fare Card for 190 CHF. There are a few more hoops to jump through. The card is on a Swiss Pass Card which must be mailed to you, but if you are in the BO for 5 weeks, it should be no problem. You get a temporary card to cover you for the 10 days mailing time.

You might find it a better deal to get a season Jungfrau Pass for 449 CHF with the Half Fare Card, rather than multiple BOR Passes.
https://www.jungfrau.ch/en-gb/unlimited-jungfrau-summer-pass/#2289

History Traveler recently reported on the process for getting a one-month GA card, which would be similar to getting an annual Half Fare Card. I quote his report here:

OK, I promised an update. IT CAN BE DONE!! We arrived in Geneva yesterday and purchased a 1-month GA Travel Card that became active today. A few details:
We opted to go into the SBB ticket office right there in the Geneva Airport. It was very quiet, and there was a nice, helpful young women took care of all the details.
For the photo, she sent us a text message with a link to take our photos on our phones. For whatever reason, that never arrived, so she just took our photos right on her own phone! Like I said, very helpful.
We had worked with one of our accommodations to have the red cards delivered to that address in about 10 days. I'll give another update when those arrive.
In the meantime, we have a temporary slip of paper with a QR code good for two weeks. It is about the size of a passport page, and since it is so valuable, it is paperclipped inside our passport to show on transit. We won't lose that paper!
We have the SBB app on our phones, and created accounts using the Customer Number on our paperwork. That all worked, and it shows our one-month valid travelcard. Oddly, it does not generate a QR code for the one-monther. I wonder if that will happen after our travel cards are processed/created?
Bottom line, this was a HUGE savings -- hundreds and hundreds of dollars -- over two 15-day passes. If you are planning long-term travel in Switzerland and don't mind losing the free museum component, go this route. IT CAN BE DONE!

This is thread it comes from.
https://community.ricksteves.com/travel-forum/switzerland/walkup-in-person-purchase-of-a-ga-travel-card-steps-requirements

Thanks so much for these replies. I have never heard of the GA card. Where would I find the info on this? The Jungfrau season pass won’t work for us as we will be spending a lot of time over on the Lake Thun side as well, and that pass is not valid there. Also did not know about additional hoops for the annual half-fare card.

Of course, with the Half Fare Card, those trips from Lake Thun are cheap. The Jungfrau Season Pass gives unlimited rides to the Jungfraujoch.

The 1-month GA card info is here.
https://www.sbb.ch/en/tickets-offers/travelcards/ga-travelcard/ga-1-month.html

Thank you! All this is so helpful.

Are you positive you've done the math on the Unlimited Jungfrau Pass + the GA year HFC? We live in Murren for the summer so it's what we do and even with the things it doesn't cover around the lakes, it's a clear choice for long term stays.

For example, if you do 4 passes to cover 5 weeks, that's close to 1500 chf per person with the HFCs. If you do the Unlimited Jungfrau Pass for 449 chf + the GA year HFC that's around 640 chf. Are you really going to spend 800+ chf per person on things not covered around Lake Thun?

Thanks everyone! This gives us all the info we need.