Why does my laptop keep crashing or its WiFi keep failing?

I purchased this laptop in 2013 September. Within 8 months the laptop began to crash very often (especially when moved) and the wifi would often show 'no connections' for no good reason (restarting would sometimes enable it to discover wifi networks again). I sent it to repair at ASUS warranty and when it came back, the harddisk and motherboard were both replaced. It worked fine for another year. And now (around 2015 September, so approximately 2 years after purchase) the laptop has again began to crash (again, most often when it is moved) and fail its wifi like it did the first year.

What could cause it to keep behaving like this, even after repair and replacement of most major parts? Do I repair my computer (warranty is over so has to be with my own money this time) or shall I just buy a new expensive laptop that would last me atleast 4-5 years without these problems>