Most applications use a 1.3mm key travel.
Where you need fast data entry choose 0.8mm travel.
In applications where an accidental key press could cause problems (such as an alarm pin pad) use a longer key travel, typically 1.5 to 2.0mm.
Some examples of key travel recommendations are:
Eftpos Equipment: 1.0~1.5mm
Alarm Panels: 1.5~2.0mm
Medical Equipment: 1.3~1.8mm
If you are using your keypad over a pcb mounted switch please indicate the switch travel plus clearance between the bottom of the key and the top of the switch.