Should I follow up again after a final interview? What's the longest you've waited for a formal offer?

I had a final round interview with a boutique asset manager for an analyst role about 3.5 weeks ago. The interview lasted 2 hours and I met the CEO, COO, and other members of the team. Prior to this final interview, I had 2 phone interviews, an in-person interview with the CIO and analysts, and completed an excel/finance test. I felt the interview went well as they asked when I could start, went over basic benefits, and even gave me some insights into a strategic partnership the firm was looking into.

I sent my initial thank you emails after the interview. including an update that I recently passed of Level 2 of the CFA program. HR responded positively and said they were still considering an appropriate timeline to make a formal offer. 2 weeks after the interview, I followed up with HR again expressing my interest in the role. They responded stating they were in the midst of a transition for their strategic partnership and do not have a timeline for when a formal offer can be made. They further assured me that they want to make a formal offer and requested my further patience. Fast forward to today, and I'm approaching the 4 week mark since the final interview. The job posting has been removed from their website and linked-in since I started interviewing.

I'm curious if I should follow up again or just move on? I'm a back office rep whose spent the past year since graduation attempting to break into a FO position. I'm very accustomed to rejections and ghosting, but this is the closest I've gotten to an AM analyst role. I generally believe if you don't receive an offer within 2 weeks, you're most likely dinged. However, its odd that this firm keeps responding to my follow up. I've continued to apply and interview for other roles, however this role is the perfect situation for me. Any thoughts? What's the longest you've waited for a formal offer?