I'm a little surprised by this, actually... but here's the statute and some similar case law, thanks to The Google.
C.R.S. §14-10-122(1)(a): [T]he provisions of any decree respecting maintenance may be
modified only as to installments accruing subsequent to the motion for modification and only
upon a showing of changed circumstances so substantial and continuing as to make the
terms unfair.....
C.R.S. §14-10-122(2): Unless otherwise agreed in writing or expressly provided in the decree,
the obligation to pay future maintenance is terminated upon the death of either party or the
remarriage of the party receiving maintenance.
II. Case Law:
a. In re Marriage of Weibel, 965 P.2d 126 (Colo. App. 1998). Wife was receiving
$800 per month in maintenance. Wife was able to live frugally and contribute to
her savings every month. Husband filed a Motion to Modify Maintenance
claiming that the original award was unfair because Wife did not need
maintenance. Husband did not argue that he was unable to afford the
maintenance. A party seeking modification of an existing maintenance order
bears a heavy burden. When determining a motion for modification, the trial
court should not consider whether, based on the current circumstances, it would
have awarded a different amount of maintenance. The correct inquiry is whether
the original award has become unfair. The fact that recipient of maintenance has
increased his or her income, does not, by itself, make the original award
unconscionable.