The valves have date stamped information on them to indicate the date of manufacture, these molded components will usually ship from the assembler within 4-6 months to the distibutors, and the distributor should rotate their inventory in no more than an additional 6 months. If you get a Fleck valve, let me know which one and I will tell you where the date stamp code is so you can see if it within the 1 year mark that is considered normal. The 5 year warranty starts from the date of purchase according to your receipt, not more than 1 year after the date code, without reciept, the date code becomes your warranty start date. While this is not set in stone, it is very common for most manufacturers. Some will only give a 6 month window from the date of manufacturing.
Last year we found a box of 48 Fleck 5600 metered valves in the storage area, hidden in a corner. The date stamp showed them to be over ten years old, so... these went to the garage sale rack, no warranty, for $75 each. They sold out in the first half hour we put them out.