A question on AMD durability & Stability

[Game-Hacker]

I have one old computer that I did not use anymore for more than 2 years. I decided to give it to my 11-year old nephew.

The spec:

ECS K7S5A
AMD Duron 1 GHZ
Riva TNT 32MB
128 + 64MB SDRAM VISIPRO 8ic
20 GB Seagate RPM 5200
Sound on Board
Sony CD-Rom
Floopy
Using WinME

Now, when I used to use that computer, it ran ok but now, It seemed to be slower than before. My question is: Is it true that AMD processor stability and durability decrease after certain year?

I also use the following computer in my office:

AMD Sempron 2.8
ECS KT-600A
Geforce FX 5200 128 DDRRAM
2X 512 DDRRAM Visipro 81c
Seagate Baracudda 80GB SATA
Sound on Board
Samsung DVD Combo
Samsung Floopy
Using WinXP SP 2 professional edition

I notice the first six months, that computer ran pretty fast but now it still run fast but not as fast as before. So does time has effect on AMD in Stability and durability?

I need feedback as I am going to buy a new notebook and still confuse to choose between Prescott or AMD Opetron.