One thing that box lockers can’t do that nearly all other styles of lockers can (depending on their height) is hang garments. Box lockers allow for a maximum number of units in a small space, but are too small to hang your jacket. Garment lockers utilize box lockers, and a coat rod is mounted under the lockers between the vertical sections. This allows for employees to hang full length garments, while still being able to secure their other personal items in their individual lockers. Denver Locker
For longer term storage, there are many self storage units around the metro area. Not cheap, but then neither is paying extra baggage fees and lugging around extra stuff not needed for another leg of your trip, as it sounds like Terry might be doing. For example, I found "Downtown Denver Self Storage" with units starting at $45 a month. Denver Locker