You should not re-use the old rubber gaskets. Remove them from the swing top and install a new red rubber gasket for each bottling. A new gasket should keep its seal for up to a year perhaps longer (I don't keep them that long) they are a pretty good sealing option. I have heard of people using two new gaskets if the swing bail is getting tired but I have not tried that. Probably easier to drink some more Grolsch instead.

The red rubber seals do work as a replacement. The Grolsch ceramic top is about 1/8 inch less in height than the replacement plastic top. Thus the two holes drilled into the neck of the Grolsch bottle are further from the bottle rim than on the easy top bottles. This 1/8 inch difference makes it impossible to completely close the cap without generating enough force to shatter the bottle. This is why I stopped using Grolsch bottles.

No this will not work because the hole is too small for the cap to go through. What I finally found that accomplished a seal was simply add a second seal like the existing one over the existing seal. This creates a double thickness seal and it will stay in place when closing the cap. Put the second seal on wet. Note I push down on the cap when closing it because of the additional force needed to secure the latch. Easiest test is to use a seal from another of your bottles and find out if this works for you. Wish I could send you a picture.

They will replace the original gaskets however we have found out the the wires need a little tweaking to tighten the tops. Try this first then the gaskets.

I have only started paying close attention to this and as I make maybe 6 batches per year I am going to place a note on my calendar at the two year mark. I had a collection of bottles that included some that were 10 years old and some that were brand new and a few in between so I am going to establish a baseline that is admittedly very conservative.

Every time I bottle a cider. They’re cheap.

Depends on usage frequency but i change them once in a blue moon. Last a long time

Anytime that they look dented or deformed. I have gotten several brews out of them. I replace on the side of caution.

I usually replace every 3-4 batches as they get a bit mashed over time and I don’t want to risk losing carbonation. If I cellar for an extended period of time I’ll replace after batch 2. Hope this helps!

There isn’t a fixed replacement/lifespan number so usually just “as needed”. In fact I’ve used the same gaskets for dozens of brews without any seal issues. You’re more likely to encounter a leak when the seam on the white plastic part of the pop-top creates a small gap between itself and the gasket.