After wandering around various web sites trying to figure out whether I could get a month to month discount on our phones (tricky: we are sharing a plan with two phones that won't run out of their 2 year cycle until December), I gave up and just called Verizon. They did the usual, hey, we'll increase your data and not charge you any more money!!! dance (we don't care -- we don't use all the data we already have, so we'd rather take a decrease in money over an increase in data), then turned me over to someone who could answer the question (silly me -- called the wrong number). And while Verizon doesn't automagically apply the month-to-month discount when you become upgrade eligible (any more than they automagically apply the discount when their data rates change -- or, for that matter, automagically give you the increased data allotment. Can't blame them -- free money, amirite?), they were quite happy to apply it when I called them. Altho I had to ask for it for the second phone as well, because that wasn't done when I asked about "two" phones, they just did mine.
So. Note to self. Verizon wants you call in periodically and request the discounts you are eligible for. (In theory, it's $15/month discount on a $40 "line charge", so with two lines, $30/month savings. Which is Not Nothing.)