I had a mountain bike with DOT brake fluid for 10 years. Never flushed the fluid, never even opened the system. When I sold it the front caliper was getting sticky and making the brake drag sometimes. I told the buyer and they fixed it.

I have a mountain bike now with mineral oil brakes. Same routine, never bled or even opened the system, works fine.

I never flushed the brakes on any car I had. I had a Blazer for 18 years and I put brakes on it when I got it including rebuilding the rear wheel cylinders. The next time I put brakes on it was at least 100,000 miles later (mostly highway) and the cylinders were nasty but I just rebuilt them again. Never opened the front calipers.

I don't recommend doing maintenance like I do, however. I tend to let things go, works for me.

Some car makers recommend brake fluid flush, some don't.