How often do you replace your computer and/or laptop?
As infrequently as possible.
My desktop computer hardly ever gets used any more because my laptop is more powerful. I bought my laptop in either 2011 or 2012, I forget which. It has as much memory as the motherboard can take but I recently put a 4TB solid state drive into it. I'm hoping it will run for many more years to come.
I browse forums etc using an Android tablet that I bought in early 2014. The battery isn't very good any more and the version of Android is old enough that I keep being told to update my apps only to then be told the new version isn't compatible with old Android, but for day-to-day stuff it does the job. When it dies I'll probably replace it with a cheap laptop with a focus on light weight and battery life - it seems that if you can even find a decent Android tablet these days it runs to the fat end of $1000.