The simple answer .. as many as you bloody well like!! The kit and casting option (£89) includes the first casting. Beyond this, each time you make, you’d pay just £60 to cast in solid Silver. 

Each time you complete the process, re-order the kit refill pack (in The Makers Table); this includes both sandpapers, a new tin, returns envelope and wax .. and so, the process starts all over again. Exciting!!