The strips do work, They do need changing but that does depend on how often you open whatever it's airtight in. A friend smokes in one room in his house and he had some coins he had just sitting there on the table and In a short time they toned on one side almost gold in colour, I should have taken a pic and I have 3 handing coins myself. that been out for 2 years now, handled every day and they nowhere near as toned. so the environment does have a lot to do with it as well. smoking must add more sulphur to the air as thats what really makes the coins tone. The strips as far as i know remove the sulphur. so I think if it's sealed and you don't open for years should be as new.
The strips do work, They do need changing but that does depend on how often you open whatever it's airtight in. A friend smokes in one room in his house and he had some coins he had just sitting there on the table and In a short time they toned on one side almost gold in colour, I should have taken a pic and I have 3 handing coins myself. that been out for 2 years now, handled every day and they nowhere near as toned. so the environment does have a lot to do with it as well. smoking must add more sulphur to the air as thats what really makes the coins tone. The strips as far as i know remove the sulphur. so I think if it's sealed and you don't open for years should be as new.