I spoke with our warranty service department and the rubber button is a very uncommon repair. Obviously a lot of factors such as how your light is used and cared for can have in impact, but as a whole, the rubber modes switches are made from a high quality, durable rubber and rarely wear out.
In the event that it does wear out, Nitecore lights are covered by a five year combined distributor and manufacturer warranty. Of the warranty cases we handle, 98% are serviced stateside and are often returned in less than 2 weeks.
Hope that answers your question!