Fair value is the best available method for financial instruments but its limitations and challenges should be carefully evaluated before expanding its use beyond where it's applicable today. PwC has some guidance you can use.
Although recent market events have cast doubt on marking values to market, fair value has its place in financial reporting. It’s widely acknowledged that, despite its challenges, reporting fair value for most financial instruments, particularly assets, provides investors with meaningful information to assess a company’s future cash flows and management’s performance. But projecting the challenges of fair value reporting onto the majority of both (1) nonfinancial assets and (2) liabilities calls into question whether the capital markets are ready for more fair value. It’s time to pause, reflect on lessons learned from the credit crisis, and evaluate whether it makes sense to expand fair value beyond where it is used today.