I refuse to enter into a long-term contract for anything.
Unlocked mobile, purchased outright.
Pay Monthly SIM.
Unlocked 4G router, purchased outright.
Pay Monthly Unlimited Data SIM.
Routed through a Draytek wireless router to cover the whole house, or slipped into a pocket when I'm out and about so I don't have to use some pub's insecure wifi.
I do not get the fascination with giving some company money for doing nothing more than "saving up" on your behalf, nor with tying yourself into a commitment with a company that - at that point - you have no idea the quality of service that you will receive. Hell, I have to think twice about whether or not I should pay Amazon Prime over a year or each month (hint: Unless you pay interest at more than 37% APR, it's cheaper to buy annually than monthly over the course of a year).