I also have 6 years old laptop for similar reasons. My primary machine is desktop workstation and older machine allows me to swap hard-drive easily while travel

I also have 6 years old laptop for similar reasons. My primary machine is desktop workstation and older machine allows me to swap hard-drive easily while traveling. I can also take harddrive with me, and leave cheap shell at hotel room. Plus keyboard is unbeatable :-) But I am upgrading to skylake based laptop. It finally has 16GB RAM in ultraportable with good linux support. Old laoptop will be still usable sometimes.