I started noticing hair loss my early 30s. I have been on finasteride for about 10 years consistently, along with 5% Kirkland minoxidil. I'm now almost 42. I can tell you that my regimen has worked wonders in maintaining my hair. I still have some thinness at the crown and just behind my hairline, but I was able to recover a bit from my initial hair loss before starting this regimen in my early 30s. You can see where my new hair, likely driven by Minoxidil, is a pure brown color as opposed to my peppered brown/gray hair elsewhere. I can honestly say that after 10 years, I don't think the effectiveness has worn off. There are days where I feel like my hair seems thicker, and there are days where it seems thinner...likely my anxiety of over-analysis of whether I'm keeping or losing my hair. All in all, it seems about the same.
Regarding sides, I got freaked out too 10 years ago because of the scary things on the Internet, and I think I suffered from major nocebo thinking my erections were soft and I was getting brain fog. So, I went on, then off, then back on again, back and forth, back and forth. I finally decided to just go all in and never looked back. Do I worry about long term side effects? Sure...but nothing is proven regarding sides, and I don't think I have sides today once I forgot about the fear mongering. I'm not saying that there are some out there who don't legitimately get sides, but the mind is a powerful thing.