4 years for goods, 6 months for services
If however you effectively make a claim on your first return (ie your input VAT is greater than your output VAT), do not expect to get the money immediately, you will have an initial inspection to make sure that everything is above board. This is mainly to stop companies setting up, making a large VAT claim (often fictitious), and then liquidating, with our taxpayers money!!!
Anyway back to the thread, regarding Fuji lenses and the s/h market, the primes and the 'kit' and older zooms generally are available s/h, its the 10-24, 16-55, 50-140 that are very rare s/h, either because people are hanging onto them, or because they just are not being bought, and therefore less are available.