It kind of depends on the switch, the contact wiping action and their alloys, sealed or not etc. High current switches don't work well at low currents, the contacts oxidize more than signal kind of switches.
I would say you need enough current and voltage to cut through any passivation layer.
Automotive digital input IC's i.e.
MC33975 have programmable wetting currents 2,4,16 up to 32mA but I think this pullup value is for powering some sensors. I've seen 12V/100Ω used on windshield wiper motor switches and ign. points for ~120mA which seems huge.
If you can afford (power budget) it several mA does it. Normally you'd have a cap say 4.7-33nF across the contacts for ESD/RF which has a tiny bite for the switch. I don't like really high discharge currents on small switches. So I use 0.1uF series with 100Ω at 5V and seems to work for me.