For me it's about 2.5-3 years for a Windows laptop.
5.5 years from a VAIO is awesome.
I just bought myself a 17" Dell Inspiron for $600 and I've swapped some things out.
Threw the HDD out and replaced it with a Samsung SSD, swapped the wireless card for a more powerful one, and I am looking to get a second stick of RAM so I can bump myself to 16GB.
This is just after I had retired my old Acer Aspire with a 2nd gen i5 and 4GB of RAM. I wanted to upgrade it to Windows 10, but the lack of drivers and all is quite a pain. Still have it lying in my cupboard as a backup though.