Googlebot seems to give up crawling your site after about 14 seconds :) You might see that reported in GWT.
I know you weren't actually asking, but I figured it's worth stating this for someone else who might experience the same thing. Load times do vary greatly. Digging down into the Analytics can show you where/why they vary. And as you said and as always with Analytics, look for trends more than exact figures.
Compress data with gzip is probably the big one for modem users, but also batching scripts and CSS together, reducing image sizes, re-arranging code to reduce blocking during rendering.
These are all things under your control, and with current mobile browsers, these are things you really must care about
You can do something to make like better for those on mobile and dialup with server settings, image compression, and the like. You can't change their connection speed, but you can focus on their experience.