As a customer for at least 5 yrs or so, and paid several Tabs, the one reason I would consider paying early is if one has a Tab large ($21) and for services at $74. Can someone pay the Tab out and change their plan to a $55 one (1GB unlimited text & talk) which is exactly the same as the $74 one..or am I wrong there? (which admittedly I am very unfamiliar with switching up as I was always a medium customer). I recently changed to a Tab large and the monthly services charge is increased from $55 to $75 for what I can see as the exact same features. Not a big worry for myself, as I will pay the Tab out when the option becomes available but still may be something to look at if I am correct on the little difference in plans.
As a side question, how long is the wait to pay the Tab off if you've been a customer for many years. Is the 90 days linked to your account or your phone in late 2017?