This is the OP. Hard to believe it's been only a month since I joined here. A lot has happened already, so I thought I'd post an update.
I did a lot of thinking and soul searching and realized that my fear of rising housing costs was not as hypothetical as I thought. I've been considering moving for a while now but have been resisting because of what a great deal my current place is. It's a rental that's way below market rate, with other advantages to boot.
However, it's often noisy, both inside and out, and this is not what I imagine as a relaxing post-FIRE living arrangement. There are other downsides too, though they aren't so much the point now.
I have known all along that moving would be expensive, whether buying or renting. But when the great deal you have is not what you want, you have to compromise and decide what the next-best option is worth. I guess this is where the difference between frugal and cheap comes in.
To cut to the chase, I'm moving. I'm voluntarily -- right now, not in some imagined future -- more than doubling my housing costs by moving to a quieter location and a much newer building (10 years old vs. 90). The new place is somewhat luxurious (by local standards), made of stone and concrete (instead of thin plaster walls), and, according to some friends who have lived there, very quiet. Again, it is more than twice the rent, so it had better be nice and quiet. It's also in a good location, still within walking and biking distance of everything.
This will raise my annual spending from $22K to somewhere between $28K and $30K. That's still less than 3% of my $1.2M portfolio, probably about the limit of my comfort zone for now.
In my soul searching, I realized that major life transitions are supposed to be scary. They are supposed to pull us out of our comfort zones, challenge us to face our fears, etc. The way I see this, I might be spending more, but I will continue to be frugal. Just maybe less cheap. And maybe, in the process, I will learn to trust the system that I put in place 30 years ago when I started to save and invest for retirement.
It's only a year lease to start, so if I don't like it, I can try something else next year. I'm starting to pack now and will move in two weeks. Wish me luck. Time to test the system.