Interesting video below.
Chris confirms that even after applying all browser and Operating System patches (which will have happened by now if you have auto-update on) your PCs, tablets and phones still aren't totally secure. His advice is that when entering sensitive data (such as for on-line banking) you should cycle power before and after doing that, and not do any other on-line stuff in the same session that you've entered the sensitive data.
This applies to phones and tablets as well as PCs - most of us don't turn these off normally, partly because it takes them ages to reboot.
Another option is to use a Raspberry Pi for your really sensitive data sessions - the Pi is probably capable of running most browser-based on-line banking things, and it's immune to the Spectre and Meltdown flaws.
Interesting that he says 2018 will be the first year in computing history where, on average, computers become slower. He also predicts that computer and chip manufacturers will use these flaws to drive a marketing surge once new immune processors are developed.