An LE that sells out at the casino, may be obsolete to you, but it is not obsolete to the casino, as they will still cash it in. The only obsolete LE's are the ones from the Lady Luck and a couple other casinos that recalled LE's.
Obsolete to me is: No longer available at a casino and no longer redeenable at a casino under normal circumstances. (Caesar's is an exception) I have seen the FQ's cash 20 year old chips for customers. It depends on who the customer is and what/how much he is playing. Once they are cashed, they are put in the box for obsolete chips and sent for destruction to Silver State Disposal. Per Nv Gaming Regs.