I think you would see a degradation of performance when you started to wear through the gold finish and into the copper/nickel underneath. The best way to get around this would be to put on as much gold as you can, but this gets expensive.
Golden Rule No.3: Gold Coatings Can Be Used For High Durability
Coating a contact with pure (i.e. soft) gold generally results in a
connector with low durability and high insertion forces (i.e., high
coefficient of friction), especially when the thickness is greater
than 0.13 microns (5 microinches).
In practice, gold coatings are usually hardened by adding small
amounts cobalt or nickel to the gold. Such coatings are defined as
‘hard gold’ and produce coatings with a low coefficient of friction
and excellent durability characteristics. Hard gold coated contacts
can generally withstand hundreds to thousands of durability cycles
without failing.The durability of hard gold coatings can be enhanced
by using an underlayer having a hardness value that is greater than
that of gold and which will provide mechanical support.
Nickel is generally recommended as an underlayer for this purpose.
Lubricants are also effective at increasing the durability of gold
coatings. Generally, lubrication can increase the durability of a gold
contact by an order of magnitude.
Source: Technical Report Golden Rules: Guidelines For The Use Of Gold On Connector Contacts
In my experience a hard gold finish usually works best with anything gold, but is also more expensive. Evaluate the tradeoff of cost vs quality.
How long will it last? You'll have to test it yourself. However it's worth knowing that standard connectors (that are not on the PCB end) have 30um flash and still function through 10k cycles:
Two key factors:
Contact design: Major effect on the durability of the spring force, will eventually reduce to a level that will not give good contact. Gold plating: Thicker the gold, longer it takes to wear out.
Number of mating cycles:
USB2.0 Full Size: 1,500 mating cycles, gold flash plating.
USB2.0 Mini: 5,000 mating cycles, 15µ” gold plating.
USB2.0 Micro: 10,000 mating cycles, 30µ” gold plating.
USB3.0 Full Size: 5,000 mating cycles, 30µ” gold plating.
USB 3.0 Micro: 10,000 mating cycles, 30µ” gold plating.
Type C: 10,000 mating cycles, 30µ" gold plating.