Josh,
During normal operations, reverse thrust is usually discontinued below 60 to 80 knots. My employer directs us to begin stowing the reversers at 80 knots, and have them stowed by 60. In an emergency or when absolutely necessary, the reversers can be used all the way to a full stop. A high speed rejected takeoff might be such an occasion.
The primary reason for stowing reversers below eighty knots or so is that as the aircraft slows, the potential for exhaust gas re-ingestion increases, as well as the potential for reverse flow gasses to cause or permit foreign object ingestion. Direction to stow reversers is there to protect the engine. Ingestion of exhuast by products can cause a flameout, and some engines aren't very stable in deep reverse at slow speeds; they may compressor stall and flame-out on their own. Reverse thrust isn't very effective at low speeds, and offers little advantage.
Wheel brakes are generally employed soon after landing, but the circumstances dictate when and how much braking is used. If the airplane is light and it's a long runway with light traffic, very little braking may be used, instead preferring to allow the airplane to roll to the end while using reverse thrust.
In other cases, operators use "autobrakes," which apply braking at a preset value upon touchdown. Autobrakes have settings that correspond to acceleration values. For example, an autobrake system set to "medium" may slow the aircraft at a rate of 6 feet per second per second; if reverse is applied at the same time, the airplane still slows at the same rate, but the brakes get used less (and therefore aren't as hot; an important consideration for short turn-arounds).
We calculate our landing performance based on autobrake settings, because these give known rates of acceleration (deceleration, if you will), and therefore predictable stopping distances.