90 minutes on a regular basis could be interesting. I've only had a session that long a handful of times (and never with my current therapist) but it does seem like doing it consistently could facilitate some interesting work if you felt like that offered enough containment for you. The times I've had 1.5 to 2 hour sessions, things either got pretty intense or felt like they were going in circles, but that was always as a one-off thing.

I do 50 minute sessions twice a week, and I find that works much better for me than once a week. Don't think I'd personally want to do 90 minutes once a week, since for me it would be very hit or miss and would put a lot of pressure on that single session.