The base aim time on shortbows, longbows, and crossbows are 0.2s, 0.3s, and 0.8s, respectively. Aim time cannot be less than zero, so further aim time reduction will not normally be seen when used with other effects. The effects do stack, however, and can be seen by stacking 0.2s and 0.3s Rapid Aim items when using Aim. Repeater gloves are mainly useful because they can reduce aim time to zero when using Aim, which adds 1.5s to aim time, and compensate for the Haste aim time bug, which increases aim time by 0.8s instead of reducing it.
It is possible to upgrade the Repeater Gloves by selling them to Mikhael Dryden.