Does a man become resistant to finasteride over time?

I am a 23 year old man who recently received a scalp miniaturization test at a hair loss clinic. I was told the hairs on the top of my head are about 85% the density they should be.  If I’ve learned anything from tressless, it’s that prevention is key. My only fear about starting FIN or DUT is that my body will build up a tolerance to them. I want to take these drugs my entire life, but I’m worried that if I start before I actually begin showing symptoms, they’ll lose effectiveness by the time I really need them.  I see a lot of posts about people thinking they’re building up a tolerance to FIN after 6 or 7 years, but that might just be that their hair follicles are becoming more sensitive to DHT.  Does the drug itself build a tolerance in your body? If so, should I start with FIN and switch to DUT when I need it? Or will a tolerance to FIN also give me a tolerance to DUT?

No concern. These drugs block the DHT at the hormone receptor and they continue to work for years. This is the critical time for you if you want to see benefit from finasteride as the older you get, the less the benefit you will see when it comes to reversal rather than just slowing or stopping the process.