Do fly sprays have expiry (best before) date?

[Scarlett 001]

Do most fly sprays last more or less til whenever? I see no expiry date on mine from last year. Will it still be effective this year, or should I buy a new bottle to be sure?

Thanks!

[Adk_Katie]

I mix mine from a concentrate and it gives a "best if used within x days of mixing." (Sorry I can't remember what x is)

I would say if the bottle doesn't say don't worry about it too much. Most things just become less effective after their expire date anyway, not dangerous. Can you tell a difference in the effectiveness so far?