why my macbook (more than 12 mos old) needs mlb replaced? do you have reliability problems on 20

The people responding here are just other users like yourself, not Apple. If you want Apple to hear of your dissatisfaction click here --> http://www.apple.com/feedback/

I don't know what "MLB" is. You can check if this is a known issue subject to a service call: https://www.apple.com/support/exchange_repair/

Here's Apple's information on computer warranty: Mac Repair - Official Apple Support

I thought it was 2 years for major hardware but I see it is listed as being one year now. If you have AppleCare you get longer coverage but then you have to pay for AppleCare.

Hardware is expensive to repair now. It used to be all that had to be replaced was individual components. Now everything is soldered together and replacing a failed component often involves replacing half the computer. People want small and light but that's the downside to it.

It's like casinos. in reverse. The only guaranteed winner is the casino. A few people will be lucky and walk away with more than they spent, but most won't. So if you don't get Applecare and the model has problems that don't merit a service bulletin (recall) you'll kick yourself. If you're like us with iPhones, we never get Applecare and over the span of owning 4 low-end iPhones we have saved enough to buy our next iPhone with the savings. On the other hand if you don't get Applecare and then 1 year and 1 day into service it has problems you will be royally annoyed at Apple when you see the $800 repair bill and wish you had spent $200 for Applecare. You gamble.

Two more aspects. One is modern computers don't have parts that can be replaced, and those that can cannot be done by the user. Gone are the days when you could pop in a $50 part you bought at the local computer store. Now it's a $500 board that only Apple has and only they can replace. So repairs are very expensive. That leads onto the next thing which is your comfort level. Some people cannot afford a $700 repair bill. Kind of like insurance deductibles. Statistically you pay more in the long run for a low deductible policy but then you're never asked to pay more than $500 if your car is in an accident.

As for the computers themselves, it is hard to tell. Apple has always considered something 7 years or older to be obsolete. However, many of us have had Macs from the 1990s and early 2000s that lasted two decades or more. However, and there is no real proof to this, I kind of get the feeling that newer Macs do not have the metal parts and truly the quality lifespan of the old ones. The M1s are just being produced so nobody knows. Things get tested but the real test is when millions of users have something for a year or more. So I guess that while maybe I might not buy Applecare for a new iPhone, I might consider it for a computer, particularly if it was a new model. I tend to play it safe and I have never in my life owned a computer less than 4 years old so it has always had some road testing before I buy it, plus it is cheaper than new. ;-) I don't game or do high end things and it was only last month I graduated from a 2008 computer to the 2012 model I am using now!

Also check if your credit card company has an extended warranty. I believe ours will extend a manufacturer's warranty by one year on anything we buy completely with the credit card.